And with that, I'll turn it over to you, Patrick.

Patrick Williams -- President and Chief Executive Officer

Thank you, David, and welcome, everyone, to Innospec's first-quarter 2019 conference call. Once again, I am pleased to present another very positive set of quarterly results for Innospec. We've had a strong start to 2019 and have laid great foundations for the remainder of the year. All the key metrics of our business have improved.

Sales were up 8%, operating income is up 25% and adjusted EPS is up 23%. This performance has enabled the board to approve a further increase in our semiannual dividend to $0.50 per share. We have now increased this dividend every six months since its inception in 2013. Our strategy continues to stand the test of time, meeting the changing demands of our customers, markets and the environment.

We have delivered this performance with some significant headwinds. Not only did we have zero octane additives sales, but we also had increased costs relating to share-based compensation. We have accrued for these costs in the quarter. The impact of this alone was $0.23 of EPS, emphasizing the underlying strength of the business performance.

Fuel specialties had a very good quarter with customer activity helping drive good volume growth. A richer sales mix pushed gross margins up toward the top end of our expected range for this business. Importantly, we delivered 17% increase in operating income with all regions contributing to these results. After two years of excellent growth, performance chemicals had a quieter period with volumes flat against a very strong first quarter in 2018.

In addition, revenues were negatively impacted by currency exchange rates. However, the margin improvement projects that we have been working on are delivering with a further 2-percentage point increase in gross margin. The business has also controlled its ongoing costs, resulting in a 12% improvement in operating income. We continued to invest in R&D and increasing demand for our sulfate-free innovative technologies shows that we are meeting the customers' and market's needs.

The market for oilfield services continues to be volatile and challenging, but we have outpaced our competition in delivering a 23% increase in sales. We have delivered this through a combination of growth with existing customers and expansion with new customers in our target basins. Although sales mix resulted in a slightly softer gross margin, we have controlled our costs, which has resulted in an operating income up 160% over last year. There were no sales of octane additives in the quarter, which we have previously indicated.

We have no further confirmed orders from our remaining customer, but we have indications that there may well be one final order toward the end of Q2 or early Q3. Now I will turn the call over to Ian Cleminson who will review our financial results in more detail, then I'll return with some concluding comments. After that, we will take your questions. Ian?

Ian Cleminson -- Executive Vice President and Chief Financial Officer

Thanks, Patrick, and good morning, everyone. Turning to Slide 7 in the presentation. The company's total revenues for the first quarter were $388.3 million, an 8% increase from $360.7 million a year ago. The overall gross margin increased 1.3 percentage points from last year to 30.3% driven by improved margins in both fuel specialties and performance chemicals.

Adjusted EBITDA for the quarter was $51.7 million, an 18% increase compared to last year. Our GAAP earnings per share were $1.17, including special items, the net effect of which decreased our first-quarter earnings by $0.08 per share. A year ago, we reported GAAP earnings per share of $0.90, which included a negative impact from special items of $0.12 per share. Excluding special items in both years, our adjusted EPS for the quarter was $1.25, a 23% increase from $1.02 a year ago.

Moving on to Slide 8, revenues in fuel specialties for the first quarter were $156 million, a 9% increase from the $143.4 million reported a year ago. Volumes were up by 8%, which, together with a positive price/mix of 5%, was partially offset by an adverse 4% currency impact. Good customer activity and new business wins have driven growth globally, notably in EMEA. Gross margin for the quarter was very strong at 35.7%, up 1.9 percentage points from the same quarter last year and at the upper end of our expected range.

Operating income for the quarter in the segment was $33.9 million, up 17% from $28.2 million in the first quarter of 2019. Turning to Slide 9, revenues in performance chemicals for the first quarter were $118.1 million compared to $124 million last year, a decrease of 5%. Overall volume and price/mix were flat and there was a negative currency impact of 5%. Gross margins of 22.5% were up 2 percentage points over the first quarter of 2018.

Operating income for the quarter was $13.5 million, up 12% on the $12.1 million in the comparative quarter. Moving on to Slide 10, revenues in oilfield services increased 23% over the same quarter last year and 5% over the strong fourth quarter of 2018. Increased customer activity drove a volume increase of 6%, and this was combined with a positive price/mix impact of 17%. Gross margin suffered slightly, up 33%, down 0.8 percentage point on a comparative quarter.

Operating income of $7.8 million was more than double the same period last year. Moving on to Slide 11, as we expected, there were no sales of octane additives in the first quarter. As a result of this, the business made an operating loss of $2.8 million in the quarter compared to an operating loss of $1.4 million a year ago. Turning to Slide 12, corporate costs for the quarter were higher than expected at $15.2 million compared to $13 million a year ago, driven mainly by accruals for share-based compensation as a result of the 35% increase in our share price during the quarter.

We expect to normalize corporate costs between the range of $12 million to $13 million per quarter. The effective tax rate for the quarter was 26% compared to 25.3% last year, reflecting the geographical mix of the business. And we expect the full-year effective tax rate to be approximately 27%. Moving on to Slide 13, this has been a good first quarter for cash generation.

We delivered cash inflow from operations of $13.2 million in contrast with a small operating cash outflow of $2 million in the same quarter last year. Capital expenditure was $11.2 million for the quarter, which included $3.8 million for the purchase of the land and buildings at our manufacturing site at Herne, Germany. As at March 31, Innospec had $123.5 million in cash and cash equivalents and total debt of $210.4 million, resulting in net debt of $86.9 million. And now I'll turn it back over to Patrick for some final comments.

Patrick Williams -- President and Chief Executive Officer

Thanks, Ian. Over the past 18 months, we've been very focused on three strategic elements, maintain solid sales growth, improving margins and investing in organic growth projects to provide a solid foundation for 2020 and beyond. I'm pleased to say that we have made great progress on all three fronts. In an environment where global markets are suffering from doubts over economic growth, concerns over tariffs, Brexit and other geopolitical issues out of our control, we have continued to stay focused on innovation and organic growth.

This has paid dividends in all of our markets. We have experienced the first early commercial sales in each of our key three organic growth projects. While these are really promising, it is too early to quantify how big an opportunity each of these represents. Sales and margins have improved during -- driving impressive operating income and EPS.

An increase of 23% in adjusted EPS is excellent despite the substantial accruals for share-based compensation. Operating cash flow in the quarter was positive, which contrasts with the previous first quarters. Our balance sheet remains in great shape even with capital expenditures being a little higher in the quarter. We continue to invest in organic growth projects, and we took the opportunity to acquire the land and buildings on our site at Herne, Germany.

This site is strategically important and this was a cost-effective alternative to leasing. I'm also pleased that our Board has approved a further increase in our semiannual dividend of $0.50 per share, which continues our ongoing record of dividend growth. We have strong and consistent conviction about executing our business strategies and this is producing great results. We will continue to focus on organic growth to develop further innovative technologies while being open to any acquisition projects, which add to our business or offer a more transformational opportunity to Innospec.

We are confident that our prospects for the rest of 2019 and beyond are very attractive. Now I'll turn the call over to the operator, and Ian and I will take your questions.

Questions & Answers:

Operator

[Operator instructions] You first question comes from the line of Jon Tanwanteng from CJS Securities.

Jon Tanwanteng -- CJS Securities -- Analyst

Nice quarter. Patrick, IMO 20 is -- 2020 is about six or seven months away here. What are you expecting now from a demand perspective? And are you prepared to scale the production? What's incremental margin on the sale of those sulfur additives?

Patrick Williams -- President and Chief Executive Officer

Yes, Jon. Good question. We're just starting to see an uplift in sales in the IMO 2020 product. I think it's really started to take effect in the general markets that this is coming upon us very quick.

And it's hard to say what's going to look like, but those margins in that area are much higher than the fuel specialties margins. I think the volumes are to be known. But we did get sales in this quarter, and we expect sales in the remaining quarters moving forward. To what magnitude? As I said, we'll see toward the end of this year.

Jon Tanwanteng -- CJS Securities -- Analyst

OK. Great. And maybe I missed it, but what's driving the strong margins in Fuel Additives this quarter? And can we extrapolate that going forward?

Patrick Williams -- President and Chief Executive Officer

Some of it was product mix. Some of it was we're starting to see, like I said, the IMO 2020 product come through. But I would still stick with that 33% to 34% because you do get some variances upon quarter. But it was a nice quarter, and we'll continue to see how the markets mature in some of these areas that we're talking about and that will drive potentially margin improvement.

Jon Tanwanteng -- CJS Securities -- Analyst

OK. Great. And then, Ian, the operating loss in Octane, how should we model that going forward especially if we assume that the shipment coming later this year is going to be the last one? Does that fall off pretty quickly once you sunset that business? How do you roll that up?

Ian Cleminson -- Executive Vice President and Chief Financial Officer

Yes, Jon. Good question. In Q1, we've had zero sales and we've also slowed the manufacturing facility writedown to manage our inventory and working capital. Because of that, we've had to take some of those costs to the income statement rather than into inventory.

So this is very much a worst-case scenario of a flat business. Once the business completes and we step out of the market, we'll treat the octane additives segment as discontinued and it won't form part of our ongoing results. So once we start production, a lot of those costs will go away.

Jon Tanwanteng -- CJS Securities -- Analyst

OK. Great. And then, finally, just on the performance chemicals, just a little color on what's driving flat volumes in pricing in that segment. Do you expect that to change going forward? Is there a stronger competition or weaker end demand? Just a little more detail on what's going on in the end market will be appreciated.

Patrick Williams -- President and Chief Executive Officer

I think part of it is we had a really strong first quarter and we had a really strong fourth quarter of last year. I think it's just order pattern. We're not necessarily seeing a slowdown in the Americas. We did see a little slowdown in the apprehension in Europe.

But overall, we're still very confident with the numbers that we've put out there in the mid to high single-digit growth with the margins that we've put out there as well. There was nothing in the quarter that surprised us. And again, as I said, we're still very confident moving forward in Q2, 3 and 4.

Operator

[Operator instructions] Your next question comes from the line of Mike Sison from KeyBanc.

Mike Sison -- KeyBanc Capital Markets -- Analyst

When you think about the volume growth in fuel specialties, you had a really good '18 and it looks like '19 is gaining even more momentum. Can you maybe walk through how much of that is new products, market growth? And then how do you think that growth kind of flows through in 2Q and the rest of the year?

Patrick Williams -- President and Chief Executive Officer

I think it's a little bit of everything, Mike. I think we've had some customer growth, organic customer growth. We've also picked up some new business. I think it's probably just a volume as well going from one quarter to another.

And I think it's also, as we said, some new technologies that we brought to the market and we started to see some sales in the IMO 2020 product. So it's really a combination of all of those that provided us growth. It's hard to say will we continue to see that growth going into two, three and four quarter. I would probably still stick with our original growth rates that we've put in there and we should see more color at the end of Q2 to see really if we're going to keep on that growth cycle that we saw in the first quarter.

Mike Sison -- KeyBanc Capital Markets -- Analyst

Got it. And then in oilfield services, clearly, that business is recovering. Where do you think profitability can continue to improve to as the year unfolds?

Patrick Williams -- President and Chief Executive Officer

Yes. I mean, you saw that we increased our operating margins significantly and that was more about controlling costs. For now, the focus is now getting our gross margins up and introducing some of the new products that we have in the portfolio as well, which have higher margins. So you'll see that continued focus on the margin profile.

The revenue growth is there. We've done a really good job of balancing our customer base. We're expanding outside of North America into other parts of the world, which will take out some of the cyclicality in this business. So the real focus right now really needs to be on margin expansion and I think you'll see that focus continue throughout the year.

Mike Sison -- KeyBanc Capital Markets -- Analyst

Got it. And then just one quick follow-up. Your balance sheet's still in pretty good shape. In terms of acquisitions or adding new technologies or businesses, how does the pipeline look? And is there opportunities for bigger deals out there?

Patrick Williams -- President and Chief Executive Officer

It's interesting, Mike. In general, just the chemical sectors, in general, we've seen the market slow down quite significantly. In addition to that, you're seeing multiple start to back off, which is what we wanted. Obviously, we don't want to chase high-multiple businesses.

We do have things in the queue, from smaller businesses that have great technology that need global expansion and really need our breadth of technology and technology personnel behind it. So you'll see us looking at some small deals that won't be transformational. But we are open to something if it comes along and the multiples are right that is transformational. You've seen the balance sheet.

We're in great shape. I think you know we don't chase multiples and we don't have to acquire to grow, which is the position I always want to put this company in. It's not having to acquire to grow and we've actually finally have gotten there. And so I think that with all the internal projects we have with some of the small acquisitions we were looking at, it should be a really good year moving forward.

And as I said earlier, if we see a transformational deal that is a fair multiple, that makes sense for us and our shareholders, we'll jump on it.

Operator

The next question comes from the line of Chris Shaw from Monness, Crespi.

Chris Shaw -- Monness Crespi Hardt -- Analyst

I just jumped off another call so I apologize if some of these have been covered. But just on the octane additives, if there really is a final order coming up, do any of those costs move into the fuel specialties segment because of I know you're still supporting the aviation business there from that same plan. Is that right?

Ian Cleminson -- Executive Vice President and Chief Financial Officer

That's right, Chris, yes. fuel specialties carries the AvTel products. We don't expect any of the octane additives costs to transfer across. We might see a little bit of gross margin erosion in our AvTel products, but nothing that will be meaningful for the fuel specialties business.

Chris Shaw -- Monness Crespi Hardt -- Analyst

And then for fuel specialties again, just how much -- was cold flow again a big impact in the first quarter because, again, it was very cold here in North America at point through 1Q.

Patrick Williams -- President and Chief Executive Officer

No. We didn't see a real push in cold flow. I mean, it was pretty stagnant compared to where it was same time last year. So nothing that was really out of the ordinary on a single product growth.

It was really generally across the board.

Operator

There are no further questions at present.

Patrick Williams -- President and Chief Executive Officer

Thank you for joining us today, and thanks to all our shareholders, customers and Innospec employees for your interest and support. If you have any further questions about Innospec or matters discussed today, please give us a call. We look forward to meeting up with you again to discuss our Q2 2000 results in August. Thanks, and have a great day.

Operator

[Operator signoff]

Duration: 28 minutes

Call participants:

David Jones -- Vice President and General Counsel

Patrick Williams -- President and Chief Executive Officer

Ian Cleminson -- Executive Vice President and Chief Financial Officer

Jon Tanwanteng -- CJS Securities -- Analyst

Mike Sison -- KeyBanc Capital Markets -- Analyst

Chris Shaw -- Monness Crespi Hardt -- Analyst

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