Changing from 5W-30 to 0W-40

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REAL BRIEF:
I drive a 2007 Volvo V70 base (non-turbo) 2.4l I-5 auto.
The car calls for 5W-30 with synthetic being preferred to keep the PCV system clean.

I'm running Mobil1 0W-40 at the moment and it appears my mileage is going down a lot.

I tally mileage the "hard way" monthly. I take total gallons and divide by total miles.

A 500 mile trip garnered me a >17 mpg quick calculation. I usually get 26-27 mpg on such trips.

Is it possible for mileage to take such a hit? I'll resurrect this thread at the end of my month. That's 2 weeks from now.
 
No. At max you may see a 1mpg difference, likely even less than that. Even if you used a REALLY thin 5W30, and the thickest 0W40, you're not going to see anywhere near that drop. Something else is wrong if your average does not come back up.
 
I doubt it's the oil. Sounds like a mechanical issue. I doubt your tires are that grossly under inflated, even if they were a 10 mpg hit is huge. FI injector problem? Is the oil level rising? Oil stink of gas? I doubt it has to do with seasonal fuel either, not that much of a hit. Have you done a UOA? Odds of the oil being the problem, I'd say about 0%.
 
I made that switch on two vehicles and nothing to report … probably want a mechanic to do some testing …
 
I just wanted to be brief by presenting my first blip of "data".

Yes, I'm aware that an oil selection couldn't possibly account for that much difference.
I'm praying it's a bad sensor or mechanical problem.

At first blush, the engine seems to like the 0W-40. It's quiet and strong.
 
Have you been keeping the lingonberry reservoir topped off? Swedish cars can do this if you don't maintain good lingonberry levels.
 
Originally Posted By: Shannow
Originally Posted By: toneydoc
check your mathematics


LOL, a month to get 500 miles ???

Good public transportation!
 
Originally Posted By: LotI
Originally Posted By: Shannow
Originally Posted By: toneydoc
check your mathematics


LOL, a month to get 500 miles ???

Good public transportation!


My guess would be poor driving conditions given the distance over the time.

Cold starts, cold operating, allowing to idle until warm, city driving while cold etc. etc.
 
Originally Posted By: Kira
REAL BRIEF:
I drive a 2007 Volvo V70 base (non-turbo) 2.4l I-5 auto.
The car calls for 5W-30 with synthetic being preferred to keep the PCV system clean.

I'm running Mobil1 0W-40 at the moment and it appears my mileage is going down a lot.

I tally mileage the "hard way" monthly. I take total gallons and divide by total miles.

A 500 mile trip garnered me a >17 mpg quick calculation. I usually get 26-27 mpg on such trips.

Is it possible for mileage to take such a hit? I'll resurrect this thread at the end of my month. That's 2 weeks from now.
If car runs well and tailpipie is clean or Grey, I would say you were ABSOLUTELY off on the calculation. Topping off is NOT good for the EVAP system BTW.

One mileage calculation will likely be in error; an average over 5-7 fillups would be required for reasonably accurate data. That just the way it is.

As a side note, I always got BETTER trip mileage if I jumped to the a higher viscosity (30 to 40). Ive never has a successful 20 - 30 jump do to the VVTi system being adversely affected.
 
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