Our profit before tax was $66.6 million, a 6.3% decrease, compared to the profit before tax for the fourth quarter of 2018 of $71.1 million.
Net income for the fourth quarter of 2019 was $50.1 million or $4.48 a share, compared to net income of 20 -- or $62.8 million or $5.58 per share for the fourth quarter of 2018.
Income tax expense was $16.5 million for the fourth quarter of 2019, compared to $8.3 million for the fourth quarter of 2018.
Sales for the fourth quarter were $582 million, down 1% compared to sales for the same period last year.
Petroleum additives operating profit for the quarter was $73.6 million, down 7.4% versus the fourth quarter of 2018.
Shipments increased 1.4% between periods with increases in lubricant additive shipments partially offset by decreases in fuel additive shipments.
During this past quarter, in addition to funding of $21 million of dividends, we spent $22 million on capital expenditures in support of our long-term capital plan.
Turning to the full year, our petroleum additives operating profit was $359 million, up 15.5% versus the prior year with our profit before tax of $332 million, up 14.2% versus 2018 and net income of $254.3 million, up 8.3%.
Full-year petroleum additive shipments decreased 5.5% versus 2018, with decreases in both lubricant additives and fuel additive shipments across all regions, except North America, which reported an increase in lubricant additive shipments and Asia Pacific, which reported an increase in fuel additive shipments.
Petroleum additives operating profit for the rolling four quarters ended December 31, 2019, was 16.5%, which is more in line with the historical ranges our shareholders have come to expect.
Along with our substantial investments in petroleum additives from both a capital and R&D perspective, we returned value to our shareholders through dividends of $82 million.
We ended the year with a very healthy balance sheet and with net debt to EBITDA at 1.1 times.
As we have stated before, we are comfortable maintaining net debt to EBITDA in the 1.5 to 2 times range.
In 2020, we expect to see capital investments in the $75 million to $85 million range.
For petroleum additives, fourth-quarter sales were $532 million.
I misspoke and said $582 million, apologies for that.

Summary:
Net income for the fourth quarter of 2019 was $50.1 million or $4.48 a share, compared to net income of 20 -- or $62.8 million or $5.58 per share for the fourth quarter of 2018.