flip flop oil changes=

[jamesmetairie]

if you just bought a 2003 corolla with 84,000 miles and the oil changes were flip flop,=10w30,,,30w50 ,etc.,etc. what weight oil would you go with??

[toyomoho]

I think Toyota recommends something like 5W-30 or 10W-30 depending on outside air temps. The owners manual has the recommended weights. Unless the car is burning oil, might try a 10W-40 if you want a heavier oil.

[bonnie*]

Winter : 5w30
Summer : 10w30

[Flashmn]

5W-40 all year through

[94_Rolla_Guy]

where you get 5W-40 i have never seen it anywhere, im assuming thats synthetic?

[Flashmn]

Store.. yes fully synth...
Then theres also 5W-50 they sell here.

[tnmk]

Don't change the main viscosity, (second number) you're bearing tolerances are designed for 30 weight. 40 is too thick. You might not see a problem right away, or you might get lucky and not see a probelm at all, but why chance it.

[Flashmn]

are you kidding me.... weight has more impact in how the oil acts when its hot, not bearing clearances. You could put 5W-60 there if you wanted, it would work jus as well as 5W-40 given the circumstances. For racing and high heat applications you want a taller upper number, because when the oil turns to water, thats when things break.

[tnmk]

That would contradict everything I have ever heard about oil viscosity from other people who know including my instructer in the navy that was teaching the class on oil. I've seen the same issue brought up on other forums and people answered back with the same info that I did. The higher the number, the thicker the oil. If your bearings are designe for a certain weight and you try to force something thicker in there, it won't flow like it's supposed to. It's like saying you could put gear oil in the engine and you would be fine.

If the oil is properly cooled it will never turn to "water" It will maintain it's viscosity as it's supposed to. If it turns to "water" as you stated then there are other problems that are the cause of it. Either that or it doesn't have the film strength it needs under the higher pressures of racing. It's a big reason why most racers use synthetic as it will maintain a more consistant viscosity throughout the entire temp range. It also has a much higher film strength.

I've heard of racers that run straight 30 wt with no problems.

Just curious, where are you getting your information? I've seen and heard about this question several times and the people that are "in the know" always answer as I have.

That includes my training in the Navy, people on "bobistheoilguy" as well as some others on other forums.

I've never seen anyone with any amount of experience make the statement you did.

[Flashmn]

Bearings generally arent designed for a specific oil viscosity. Oils are chosen from the general temperature of operation. You wont use 5W-30 near the equator, but you wont use 25W-50 in siberia either. I'm sure even newer corollas have different oils recommendations in the manual. Heck my corolla has almost all of them. Plus its ran with 25W-50 for the first 13 years of its life, then I changed to 5W-40 due to moving to scandinavia. Bearings and internals are still good as new. I think if my corolla was supposed to use 5W-30, like you say, the bearings should be dead now?
Well, theoretically gear oil could work. But problem is, gear oil has a low temp viscosity of 75... Not very good in oiling the bearings. Plus its not meant for engine use and its properties are quite different. So comparing gear oil to any viscosity engine oil is pointless and doesnt serve any purpose.

As far as where I get my information. ... I'm an automotive technician specializing in motorsports, I also teach automotive students and work at an automotive parts/chemicals dealership on weekends.

[tnmk]

Respectively speaking, I know what you do. That doesn't answer where you learned your info.
But considering what you do on the weekends leads to a better understanding of what at least should be good info.

So why is it that I've never found anyone else to say the same thing?

This doesn't make a lot of sense to me. An engine runs at the same temp (once warmed up) whether it's on the equator or in Siberia. Cold start temp is a different issue, but that's the first number which is not in question. So if bearings are designed by temp then that would mean... well I don't know what that would mean. Thermostats are set anywhere from 175-195 F (don't know C, Sorry) I don't know what the temp of the bearings would be, but I would think it would be close to that. So if that temp doesn't vary, why should the oil vary?

When you install bearings, you're supposed to check the clearance between the bearing and crank journal or cam journal or what ever the case may be. That clearance between the 2 will only get tighter as it heats up. And as stated, an engine has a set temp that it runs at. So realistically, as far as I can see, that dimension should never change. And if that dimension never changes, then neither should the oil.

[Bitter]

the 1ZZFE is more sensitive to heavy oil viscosities than the A series engines.

[daniel2002p]

im in TX and the dealer always puts 5W-30 in my corolla, its a 05 S

D

[Flashmn]

This doesn't make a lot of sense to me. An engine runs at the same temp (once warmed up) whether it's on the equator or in Siberia.

it strains the cooling system alot more, at some point the cooling system might start to be overused. Also a siberian winter, you'll have to install cardboard/something to block air going past the radiator/coolers, because otherwise it takes forever to reach operational temps. Oil also has the duty of cooling the engine, hence cars that run at high rpm/high speeds, have oilcoolers to add to the cooling efficiency.

Well.. I generally take everythign I read online with a grain of salt. Just because people at bobistheoilguy forum dont agree, doesnt mean they're all correct.

[tnmk]

I know about putting cardboard in in Siberia and a more strained system on the equater, oil coolers, larger sumps, bypass filters etc., but the main point is the same. The operating temp is essentially the same no matter where you are in the world. And just to clarify, we're not talking about racing applications. Just normal day to day drivers.

So why would you use a different oil in a different part of the world.

And I don't take everything I read on line with a grain of salt. I do however research what may sound questionable and then weigh differing opinions. It's a great way to learn real world stuff. And you are the only I have ever seen with this opinion on oil viscostiy. But if you can give me a logical reason why this may make sense, I would really like to know the answer since I sell oil part time. I'd like to think I know what I'm talking about. I don't like to pretend to know. I really like to know the truth about the products I sell.

So please enlighten me and explain this better. Cause right now what you say makes absolutely no sense to me.