By Bob Carpenter
Engine oil is so important to the operation of pickup trucks that it can be likened to blood in humans' veins. Without oil, engine parts gall and seize up. Use oil for too long and the necessary properties wear out, so your truck's engine wears out too. Good engine oil is critical to ensuring a long and happy life for your truck engine. But, as is often the case with something so important, certain myths seem to work their way into the thinking of enthusiasts. See how many of these you believe — or once believed.
1. You Should Change Your Oil Every 3,000 Miles
That's just the quick oil change places (and maybe your dealer) trying to get you to come back more often and spend money with them. Modern oils are designed to last much longer than that. The key is to read your owner's manual. The truck manufacturer knows the right answer. For example, the average recommended interval for oil changes on cars in 2010 was 7,800 miles. Cummins even suggests 15,000 miles for engines in certain use categories (not much idling, no redline use, longer trips, etc.).
2. You Should Change Your Oil Before a Road Trip
If the oil change interval is not scheduled to occur before or during your trip you're just wasting money. You should, of course, make sure that the oil level is correct and that there are no new leaks.
3. Change Your Oil When It Is Black
The quick-lube places love to show you a dipstick with black oil on it and explain that this is the reason the oil needs to be changed. So what if it's black? Modern oil is designed to trap and carry the elements that, if left on the metal engine parts, would become sludge. They are perfectly fine circulating in the oil until it's time for a scheduled oil change. Also, different additives in the oil change the color of the oil over time, even when there is still plenty of life left in it. Again, keep track of your mileage and change it when you get to the mileage recommended by the vehicle manufacturer.
4. Change a New Truck's Oil After the First 3,000 Miles
The thinking is that a new engine has a lot of metal particles resulting from the breaking-in process. While this is somewhat true, the engine oil filter and the oil are both designed to remove these particles from the system. It should be noted that Honda uses a special break-in oil in some of its engines, and the company doesn't want you to remove it too soon. If other manufacturers go this route in the future it's going to be hard as heck to convince some people to leave the oil in until directed to replace it.
5. Don't Use Synthetic Oil in an Old Engine; It Will Leak
This myth perpetuates the belief that synthetic oils are thinner and slipperier, so it will gush out of all the cracks, holes and missing gasket pieces that regular oil is perfectly happy to avoid. That's rubbish. Synthetic oil leaks no worse than petroleum-based oils.
6. Base Oils Are All the Same
While petroleum-based engine oils all use molecular chains of hydrogen and carbon atoms (hydrocarbons), the crude oil used to make engine oil is full of a complex mixture of sulfur, nitrogen, oxygen, nickel and other things that may or may not be useful as a lubricant. It varies from manufacturer to manufacturer and sometimes from batch to batch. That's one of the selling points of synthetic oils — you get the same thing every time and nothing that you don't need.
7. Extended Drain Intervals Will Void Your Warranty
Nope. If you are using an oil that has an extended life (like synthetic), your warranty can't be voided just because you didn't change the oil when the manual tells you to change a petroleum-based oil. It has to be proven that the oil was the cause of the failure before it could void your warranty.
8. Gas and Diesel Trucks Can Use the Same Oil
Diesel engine oils generally have a higher viscosity compared to gasoline engine oils. In very cold weather the gasoline engine might not be able to pump the thicker oil properly. Also, diesel oils have a higher concentration of additives, which may adversely affect gasoline engine parts.
9. Synthetic Oils Will Give You Better Mileage
It's unlikely. But there are plenty of other good reasons to use synthetics. They have wider operating temperatures, better wear protection, good shear stability and less deposit formation.
10. More Oil Is Better
If you're overfilling your engine because it leaks, you're making things worse. Increased resistance from the extra oil causes excessive heat. Some of the extra oil can get splashed into the cylinders and cause excessive oil burning, which leads to an increase in combustion chamber deposits. Either fix the leak or just keep topping off your engine oil on a regular basis.
Cars.com photos by Bob Carpenter; manufacturer images