slee18

iTrader: (1)

the dealership is probably lying about it because the still have a large amount of 5w-30 oil left instock.

I am running 5w-30 mobil1. I am sticking with it because here in the central valley it gets to about 110 and that will fry the engine oil when you are stuck in traffic. 5w-20 is great on start-up especially in cold part of the country. The oil will break down very fast in the summer heats like mine here.

Hartawan

iTrader: (1)

Is it okay to run 5w-40 or should i go change it? My engine doesnt sound as smooth, maybe its just me?

slee18

iTrader: (1)

I would, oil is too thick for OHC (overhead cam) engines. Your gas mileage probably isnt great.

kikaida

Im running 40 weight and it sounds smooth. So far i have only loss about 1-2 mpg from switching to 40 weight.

lobuxracer

iTrader: (2)

If you lost nearly 10% on your mileage, what did you gain?

kikaida

i peace of mind when i push the car.

lobuxracer

iTrader: (2)

So you don't mind the engine running hotter, making less power, and using more fuel than it should because it makes you feel better? OK.

kikaida

wow what's your problem?

btw my temp looks normal from before

lobuxracer

iTrader: (2)

My problem? I don't have a problem. I'm not second guessing the engineers who set up all the clearances in the engine and designed it to run on 5w-20 oil. You feel better because you're running 40 weight oil, but it is robbing power, using more fuel, and running hotter (check your cylinder head temps, not your gauge - the gauge is worthless for anything but grossly overheating).

I've seen guys who do this lots of times, and their decisions are based on how they feel, not how the engine performs. Your engine doesn't appreciate thicker oil and it is no better protected by 40 weight than it is by 20 weight. If you're giving up 2 mpg, that's nearly 10% less fuel mileage. Doesn't that make you wonder how much horsepower you're losing as well? Why would you want to do that?

kickin8

iTrader: (1)

using thicker weight oil does NOT mean you have more engine protection....

kikaida

humm thanks for the heads up. i'll look more into this

Janizary

Any suggestions for the HOT southwest area during the summer heat (115+)?

I just put in 5W-20 M1 EP when I bought the IS350 (with 7K miles on it at the time...have no idea what was in it, but better safe than sorry). However, when May rolls around and it starts to get hot as hell here, I'd be curious as to recommendations on weight for the summer months. Stick to the 5W-20 or what? Thanks all.

slee18

iTrader: (1)

Do you do a lot of stop and go driving or short trips?

If so I would switch to 5w-30 max. You are running synthetic so you can get away with 5w-20 in the summer. Syn oils tend to break down slower (molecularly speaking) less then conventional oil. Thus the heavier weight in the summer months.

Your good to go!

lobuxracer

iTrader: (2)

^^Lexus recommends 5w-20 under all conditions. The cooling system on the car is more than adequate to maintain normal operating temperatures under normal conditions. If you are tracking your car, you might want to run 5w-30 or 10w-30 Group IV or Group V synthetic since it needs no VI modifiers to meet the 10w-30 specs, but for street driving, the recommended oil is 5w-20 period.

tfz_hebe89

iTrader: (1)

OK, summarizing from posts above..

so, 5W-20 gives better MPG, quicker at startup, but worse for track racing?
5W-30 has better performance for track racing? it is heavier so slower at startup (maybe this is why the gauge is so slow to go up in cold start)