Here’s the latest reader question, along with my reply!
Larry asks: Here is another piece of lunacy, under the religion of the EPA’s CAFE holy grail. I recently bought a 2018 Tundra 5.7L V8; in the owner’s manual is the phrase: “recommended” use of 0W-20 or 5W-20 in the engine for “better, more efficient start ups, better fuel economy” – right in the manual! No mention of using – or not using – heavier weight oils. They – the auto manufacturers – can eek out another 0.25 to 0.5 MPG, is what I have found in my research. It supposedly reduces engine drag caused by the heavier weights of oil that used to be recommended; 5W-30 was recommended primarily by Toyota engines prior to 2008. What I cannot find out for certain is if I can still use 5W-30 – I think I can. Can you help here? Many peeps on two Toyota forums say their Tundra’s rings were cooked because of the lighter oil – and more oil burning as a result. Thanks to Google search, I am sure I cannot get valid information. Same holds for a 2009 Corolla recommending 5W-20; it burns oil – which is part of the design I believe. Either way, it’s asinine!
My reply: The car companies are, indeed, desperate to squeeze out even fractional increases in gas mileage as well as fractional reductions in emissions, which these very lighter weight oils help them to achieve. They facilitate quicker starts and faster warm-ups as well as decrease drag, as you note. But they are also very . . light, relative to what was usual 15 or 20 years ago. Which is part of the reason they’re also usually synthetic. The synthetics offer more protection in extremes (heat/cold, high load, etc.). But you pay extra for them, a hidden cost of the “savings” on gas.
Can you use a different (heavier) viscosity oil? Yes – and probably it won’t cause any problems. But, it might. If the engine has a variable valve/cam timing system, for instance – as many Toyotas do. These systems use oil pressure and oil pressure can be affected by heavier oil, especially during initial warm up. It may not cause any problems at all. But if it does, and the oil is thicker than what the manufacturer specifies, any warranty claim might be disallowed on that basis.
Given the huge buy-in cost (and repair costs) of modern vehicles, I’d err on the side of conservatism and use the heaviest recommended grade (i.e., 5W-20 for the Tundra) and abide by the “severe use” changeout schedule or once a year, regardless of miles.
I will also put in a call to an engineer friend of mine and get his thoughts, under the table, about this as well.
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