5w20 & 5w30

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Can you use 5w20 for a car that calls for 5w30? I have a 2008 Lexus IS350 that calls for 5w30 and I've been using Synpower 5w30 since new. I know there have been numerous discussions on the IS forums on whether you can use 5w20 or not because there was a supposed TSB for the 2006 model (same generations as the 2008) that told the dealers to switch to 5w20. I've already read the viewpoints from the car-obsessed guys (e.g. "better mileage with 5w20" or "stick with manufacturer recommended 5w30 or you'll be sorry"). I would also like to hear the opinions from the oil-obsessed folks too.
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I would only use the 5W-20 in the winter and stay with a 5W-30 the rest of the time.

While manufactures might be altering their recommendations on oil weights to me CAFE, their engines are largely still the same. Common sense tells you that hot climates like Florida call for a thicker 30-weight oil in the summer.

Personally, I use 0W-30 from Amsoil year around in all my vehicles and don't worry and protection in the cold or heat.
 
Originally Posted By: gfh77665
You are in Florida. What on earth are you trying to "gain" by using 5-20?


Not trying to "gain" anything. I just happen to have more 5w20 (currently sitting on 210 qts) than 5w30 (104 qts) and I was wondering if the car would be harmed if I used 5w20.
 
Originally Posted By: hemitom
Try mixing the two together


...........Mix in the winter and not the summer.
 
Probably won't help or hurt anything. Lots of dealers just dump a single viscosity oil in all the vehicles that is "close enough" to cut costs. If the newer ones are using 5w20, they are probably just using that in all the cars they are servicing.The Hyundai/Kia dealer that I used to get oil changes at always used Kendall synthetic blend 5w20 and Hyundai filter on my 2001 Accent which did not spec 5w20 and it did not cause any issues. I never even realized it until years later when I was going through the service records when I was selling it. I have used both 5w20 and 5w30 in both conventional and synthetic form in my Caravan and found no noticeable gas mileage difference. I wouldn't expect to see a difference by switching to 5w20. That being said, if the store were completely sold out of 5w30 (unlikely) I wouldn't drive across town in search of it, I'd just grab the 5w20
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Can never go wrong with manufacturer recommendation. They built the engine and debated the exact same application for what weight oil to use.
 
you can usually go thicker but not thinner than recommended.

at least not without an oil temp/oil pressure gauge.
 
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I see no problem if you wanted to go thicker, but the manufacturer didn't say you could go thinner for a reason, so I would stick with 5w30
 
My KIA dealer put in 5w-30. Another one uses 5w-20. Manual says both grades are fine for a 2006 Kia spectra. They both use Mobile clean/super 5000 conventional, forgot what it's called now.

One thing they both do is put a 3K oil change reminder sticker on, which gets thrown in the trash. I'll be [censored] if that oil is not good for at least 5K for that car.
 
The difference in operating viscosity between a thin 5W-30 and a thick 5W-20 is pretty insignificant.
I'd doubt that a 5W-20 would hurt your engine in any way, but given where you live, I doubt that it would be of much help either, unless you rarely drive the car far enough to get the oil up to normal operating temperature.
I'd probably be happy just to use a 5W-30 in Florida all year.
If you lived up here, a 5W-20 might be better for winter use, but you don't.
You could probably use either oil with good results and no significant difference in wear in any climate, though.
The recommended oil grade for any engine seems more related to its expected use and maker's philosophy than it does to any real mechanical differences.
You could email Toyota and ask them whether a 5W-20 is okay in this engine.
They would know better than I or anyone else here.
 
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