Going from 5w30 to 5w40?

[zeke1985]

2005 Chevy Malibu Maxx lt v6 3.5, 145,000 miles. Lots of city stop and go driving. Anyway I have been talking to a rep from liqui moly about oil recommendations, he told me to use 5w40 in my car since it's higher mileage even though it calls for 5w30. Also he said it wouldn't hurt my oil seals to switch from using a non high mileage oil, the people at pennzoil also said this. Do both of these sound right? Thanks.

 

[salesrep]

Seals will not be a problem switching. I’d stick with the 5-30, though going to the 5-40 in all likely hood will be ok.

 

[BobsArmory]

I've done it in the past with no issues. couldn't even see a drop in MPG.

 

[Leo99]

I have been using 10w40 HM in my rav4 that calls for 5w30 for the past 100k miles. Probably going to a 50 weight once the weather warms.

I use all kinds of oil in it. The seals leak a little. They're going to leak.

 

[simple_gifts]

What problem are you trying to solve? If the answer is 'none i can think of' why switch?

 

[Alex_V]

While there's miniscule chance it'll make any negative difference, if the engine is quiet and doesn't use any oil I see no point in it - just move up to a HM 5w30. The reasons to move to a thicker oil are:
Reducing consumption from cylinder or ring wear (thicker oil doesn't get past rings as badly)
Compensating for increased tolerances between moving parts (thicker oil = thicker cushion between parts that have more slop in them than they should)
Insuring adequate protection of moving parts in higher temperatures or compensating for shear or fuel dilution which thins the oil

The goal of regular maintenance with good fluids is to prevent wear. 145K should only be about half the lifespan of a well maintained 3.5, or many other engines. If you feel you've accomplished that goal of keeping long-term engine wear to a minimum and are only using the car as it was designed to be used, then there should be no need for thicker oil.

There's nothing really special about the 3.5 - just an update of the 3.1/3.4. They'll run hundreds of thousands of miles on conventional. If oil reps laid out the straight-up facts without bias they wouldn't have a job because it's
been proven time and time again that most engines don't need $7/qt. synthetic to wear the rest of the machine they're in completely out from around them, sometimes twice.

 

[SR5]

I switch between 5W30 - 10W30 - 0W40 - 5W40 - 10W40 - 15W40 all the time. All Good and never a problem. No oil leaks, no oil consumption.

My '06 GM 4-cylinder has different ignition advance depending on fuel octane used, it's about 3% power difference according to published figures. I can just feel this slight difference when I step it up a fuel grade. However I have just changed my oil from an ILSAC 5W30 (M1) to a Euro 10W40 (Penrite A3/B4), and with the oil change I can feel no difference in engine pep or fuel economy.

Sure a thicker oil technically has more viscous drag, but it's well less than 3%, and you will never notice it in regular day to day driving.

Cars don't run on one oil viscosity only, they run on a range of suitable viscosities. You will be fine.

 

[JustN89]

It will not make any difference in switching, so why bother? If you're not leaking, then your seals are holding up. The answer to stop-and-go driving is not switching viscosity in a non-GDI engine (especially to an out-of-spec oil), instead you will want to go to more frequent OCIs. With what you have described, I would run whatever was cheapest (in a 5W-30) at 6 month intervals.

 

[Oro_O]

Originally Posted By: simple_gifts
What problem are you trying to solve? If the answer is 'none i can think of' why switch?


Exactly. +1.

I wouldn't substitute one oil that works well for another with a higher content of VIIs and a lower content of, well, "oil." If I WERE to make a change, if I still lived in Louisville (used to), I would be switching from 5w-30 to a more robust, climate-appropriate oil like 10w-30. This would also address the issue of more severe service that you indicate concerns you. If you want a great oil for your climate, recommended spec, robust for hard use, and good on seals, look at M1 10w-30 HM.

 

[zeng]

What LM/Pennzoil guys say are factually correct.
Would 5W30 hurts ? No.

But I would personally 'prefer' a 5W40 LM for it's added ACEA A3B4/C3 and various Euro OEM approvals.
Do I require those Euro approvals in my Yota? No.

 

[mclasser]

I'm running Castrol 5w40 in my Infiniti that specs 5w30. No problems at all, and this car is parked outside and only used for short trips.

 

[Garak]

Yes, and I ran 5w-40 in my Infiniti, too, and no complaints, and still am running a high HTHS 5w-30, quite happily, too!

 

[mightymousetech]

Originally Posted By: mclasser
I'm running Castrol 5w40 in my Infiniti that specs 5w30. No problems at all, and this car is parked outside and only used for short trips.


Yup. Run 0W40 in my car that calls for 5W30.