Hello all. First, please forgive me because this is going to be a bit wordy. I’ve been a long-time lurker and thought I’d finally join as I have a question/concern I was hoping to have answered. I know this question has been asked before, so forgive the redundancy, but It’s me asking the question this time, wanting to hear from those who have knowledge on the subject for my own edification.
So let me begin with some minor background on myself. I’m a former Ford heavy-line tech. I worked for a Ford dealership from the mid ‘90’s to mid 2000’s. I’m not saying that to profess any kind of vast knowledge as it’s been ~30 years since I’ve worked on cars professionally and a lot has changed in those years. I love working on cars for fun but got to hate doing it for a living. Working at the dealer sucked the fun out of it and the life out of me, but it does provide some context for the question I’m going to ask. That said, I’ve done maintenance and repairs for all the cars in my family in the intervening years as it’s still a hobby I enjoy, as I’m sure is the case with a lot of you here on BITOG. It’s probably the love of cars, and likely all things mechanical that led many of us to this web forum to begin with.
I suppose I can say that I’m looking for confirmation, affirmation, validation, and perhaps absolution lol. Anyway, when I was training in Ford’s program back then, when the engineer came in to teach us on “engine theory” or whatever it was called, when speaking about lubrication, he said something that stuck with me. He basically said that the oil viscosity doesn’t matter as much as the oil spec. In other words, if the motor calls for, for example, an API SP oil (not sure what it was back then, SH or SJ maybe?) then any API SP oil (or whatever API spec the engine called for) will be fine for that motor regardless of viscosity as it will have the additive package necessary to properly lubricate and protect the engine, and that viscosity selection should be based primarily on driving and climate conditions.
I’ve followed this advice since then and it’s never failed me. But, engines were less complicated back then. Variable valve timing systems such as BMW VANOS and Honda’s VTEC had only been introduced a few years prior and were still relatively new. Ford’s modular 4.6L SOHC engine and it’s self-grenading 5.4L big brother were still relatively new for Ford. More importantly, oil grades/viscosities were still fairly simple. You had the usual suspects for most passenger vehicles which were, of course, your 5w-30’s, your 10w-30’s and 40’s, and of course the 15 and 20w oils as well. I think Mobil1 0w-30 had just been introduced around this time, and was near impossible to find, so it may as well not have existed. Of course, this is mid-90’s so internet was still in its infancy as well.
Anyway, now we come to the meat of the matter, my reason for posting. We recently purchased a RAV4 Prime for my wife, which calls for 0w-16, and I will likely be purchasing the new ’26 for myself when they come out, which will no doubt “mandate” 0w-8, despite having the same power train (or so I’ve heard). I have a hard time wrapping my head around these water thin oils. I’ve been educating myself here on this board, reading about cSt’s, HTHS, TBN etc., comparing the w-8, w-16, w-20 oils to the more traditional viscosities, and don’t like what I see. Maybe, maaaybe I can wrap my head around a w-20. For those who don’t know, all the hybrid Rav’s are built in Japan, and are both a U.S. and JDM car, so for giggles, I went to the Toyota Japan website and downloaded the owner’s manual for my wife's car. It’s in Japanese of course, but Google translate is your friend. Unlike the U.S. manual which states “must use” 0w-16 , the Japanese manual states that 0w-16 is recommended for best fuel economy, but that the engine is also “compatible” with 0w-20, 5w-20, and 5w-30 motor oils, the caveat being that they meet API SP or Ilsac GF6A specs. Kinda what the old engineer was teaching us in our class back 30 years ago.
I’ve been on various Toyota forums, but they aren’t much help. The conversations usually devolve into people stating that you must use what’s stated in the manual because the engineers designed the engine only to run on that oil, and that the oil pump is electronically controlled and programmed specifically for that oil and so on. If you read far enough through these threads, you start to see pretty quickly that most of these individuals, as well intentioned as they are, know little about cars. I’ve researched it to death, and the pump is actually a chain driven mechanical pump. The only “electronically controlled” aspect of the lubrication system is an oil pressure control valve, which from what I’ve read in various places is regulated by the ECM via info provided by oil pressure and temperature sensors in the engine. I think this myth was started by the Car Care Nut. I love his channel and am a subscriber, but even he contradicted himself in this statement in a later video when he’s tearing down one of these engines and he points out the chain driven pump.
Anyway, I guess that I’ve answered my own question, but wanted to ask those of you who know as I’ve been out of it for so long. Was the old engineer right? Will I be ok using any viscosity as long as I stick with the proper API/Ilsac spec? If that’s the case, I will probably go with a 0w-30 since I want to ensure our cars last. Her last car was 12 years old when we traded it in, and mine is about that age now. We typically keep our vehicles for at least 12-15 years and want to ensure these last at least as long.
Your input and knowledge are much appreciated.
