5w30 or 10w30?

[MaD]

At what point should I stop using 5w30, I usually go on and off with 5 and 10, but honestly, what's the difference??

 

I've heard that cars under 75K should use 5, and anything above that should use 10 because it's "Old Seal" friendly...or something.

 

My car is well over the 75k mark...And my leaks aren't TOO bad, but they exist...

 

From what I gathered, 5 is thinner so in winter it's better, and 10 is able to withstand higher temps. but If I'm using fully synthetic Mobil 1, shouldn't the 5 be able to withstand as much abuse as the 10? (Just leak all over the damn place)

 

I've noticed that when I used 10, the car seems, boggier than when I use 5. But 5 seems to affect my gas mileage??

Also, the Oil pressure guage varies with the weight.

 

Maybe I'm going insane...or it's a placebo effect, perhaps?

 

 

I dunno, please help

-MaD-

[TGPilot]

Hey MaD...

 

I am not a petroleum scientist, but I think that most cars are rated today to run 10w30 year round. I do know that the lower the weight of oil the less oil pressure you will have because, the oil molecules in a lower weight take up much less space in the oil gallies and journals (sp?) and the oil pump doesn't have to push as hard. I do find it very hard to believe that you are feeling a performance difference between 5w30 and 10w30. I use 10w30 Mobil 1 in my Turbo Grand Prix and have 0 leaks. I guess I really don't have any educated answers for you, but I run Mobil 1 10w30 in all of my vehicles year round... 8)

[MaD]

Heh, it seems that the "performance" I get is not worth the mileage I lose. The only real difference between the two is that with 5w there's not really a lag in the 4k rpm and up range as there is with the 10w.

 

It's not that bad of a lag, but 5w seems to feel "looser". As opposed to the "molasses" feel I get with the 10w

 

It's probably just a placebo effect, I think I've been over-reading the back of my Mobil 1 bottles....

 

But if there ARE any petroleum scientists out there (Shawn?, Brian?...), I'd love an answer :-D

 

Thanks,

-MaD-[/b]

[GnatGoSplat]

My car has 197k miles on it, and I use 5W30 in the winter and 10W30 in the summer. Although the manual calls for 5W30 all year, it does say 10W30 is okay. 5W30 flows better than 10W30 when cold, that's why I use it in the winter. The reason I use 10W30 in the summer is because it doesn't get cold enough that 5W would help. Since 10W30 has fewer viscosity improvers than 5W30, I just prefer to use it (fewer viscosity improvers is a good thing).

 

You should be ok if you use either one all year, 10W is good down to 0-degrees Fahrenheit I think, 5W will cover you down to the negative temps. Definitely use 5W in the winter if it ever gets below 0. 5W30 is also Energy Conserving II which means you will get slightly better fuel economy than 10W30 which is just Energy Conserving.

[MaD]

Fresh, I think I'll stick with the 5w. Even though my fuel economy seems to degrade with it. (maybe I'm too aggressive with the pedal since it doesn't bog in the 4k rpm and up range)

 

I guess I just don't like the idea of my oil presure gauge going 3 "ticks" past the middle everytime I play "go" with the engine.

(although it's usually 3 ticks under at idle, bad sensor maybe??)

 

Thanks :-D

-MaD-