From 0w20 to 5w30 lost 4-5mpg??

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racin4ds

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Hi fellas, I for one have never been a proponent of these 0w20 oils for a rise in mpg that is noticeable at least and not the manufacturers .00000001% increase study.

But I've just witnessed something with my '13 Sentra that I think may have me thinking a lil differently... It came from Nissan with FF 0w20 from what I'm told, I just had it changed at my dealer at 3750 miles as part of my free maintenance (normally ALWAYS change my own oil, but hey, its free) so I ask the service adviser what brand they use and what weight they would use and he quickly said "we don't have the 0w20 here, so we use 5w30 in everything, all Exxon/Mobil products"

Long story short I went from an average of 36-37mpg using the same fuel stations, same exact trip on my daily commute (~85miles) down to 31-32 mpg!! nothing changed but my oil. Is it possible to see that much a drop with just an oil change?

I'm sure the FF 0w20 was syn and I know the dealer put a conventional in there now but really? The Sentra has a nice little HUD with economy aids and other fancy bar graphs for tracking your mpgs and it consistently shows my measured drop!
 
No. If you get winter fuel then that will account for some of it.

Originally Posted By: racin4ds
Hi fellas, I for one have never been a proponent of these 0w20 oils for a rise in mpg that is noticeable at least and not the manufacturers .00000001% increase study.

But I've just witnessed something with my '13 Sentra that I think may have me thinking a lil differently... It came from Nissan with FF 0w20 from what I'm told, I just had it changed at my dealer at 3750 miles as part of my free maintenance (normally ALWAYS change my own oil, but hey, its free) so I ask the service adviser what brand they use and what weight they would use and he quickly said "we don't have the 0w20 here, so we use 5w30 in everything, all Exxon/Mobil products"

Long story short I went from an average of 36-37mpg using the same fuel stations, same exact trip on my daily commute (~85miles) down to 31-32 mpg!! nothing changed but my oil. Is it possible to see that much a drop with just an oil change?

I'm sure the FF 0w20 was syn and I know the dealer put a conventional in there now but really? The Sentra has a nice little HUD with economy aids and other fancy bar graphs for tracking your mpgs and it consistently shows my measured drop!
 
Yes, it's possible, especially when the weather gets colder, a thicker oil will make more of a difference. The cold weather can account for 1-2 of those mpgs lost as well.
 
I suspect there are other variables. I've ran both 0W-20 and 5W-30 in both of our vehicles, and there is little-to-no measurable difference. The engine does feel a bit slower to rev on the -30 than with the -20, but economy doesn't seem to take a commensurate hit.

What you are experiencing is a 20% decrease in fuel economy. It takes much more than a bump in viscosity grade to do that.
 
Run it for 4+ tanks, so 1500+ miles or so. Then drain (no filter change) and put in 0w20 from Wally World. If you get your MPG back, THEN, you can say it was b/c of the 'thicker' oil.

I'd say cold weather and winter gas for now.
 
4-5mpg is way too much for one grade of oil. I agree with others, mostly cold weather and winter fuel blend. Oil grade should make very little difference.
 
I could see if they went from 0w-20 to 20w50 or something.

Do your gas stations have "winter" gas? The cold weather, "winter" gas and snow tires drop the Focus from 37 down to 31 in the winter.
 
Didn't think about the winter gas blends.... bet thats most of it! We've been pretty cold here for November too so thats likely it. I do plan to put some 0w20 back in it tho just to see an apples to apples comparison... I bought the car in mid October so we were likely on summer blend gas most of the time.
 
Originally Posted By: 05foresterXT
Cold weather also makes tires lose their pressure very quickly. Low tire pressure kills mpgs.


I always monitor tire pressure, check it once a week on mine and the wifes cars.
smile.gif
 
Originally Posted By: 05foresterXT
Cold weather also makes tires lose their pressure very quickly. Low tire pressure kills mpgs.


Yep, and the fuel mixture is richer for a longer period of time as well.
 
It can be responsible for such a loss of mpg. My accord suffered the same issue when the dealer accidentally drained the engine oil (high VI Mazda with Moly 0w20) instead of a transmission drain and fill. They did a free oil change using conventional 5w20 to make up for it. The mpg hit was immediate and that occurred in warm weather.
After I had the conventional 5w20 removed and donated to my mechanic, I refilled with TGMO 0w20 SM (courtesy of CATERHAM) and presto! Mileage returned.
Pretty obvious to me what the issue was.

If a dealer told me that they don't have 0w20 so they put 5w30 in everything, I would be finding another dealer.
 
Last edited:
Originally Posted By: Roob


If a dealer told me that they don't have 0w20 so they put 5w30 in everything, I would be finding another dealer.


I see your point, but at the same time at least they're honest.
 
No way.

I have an Insight that averages 60mpg and would immediately notice any MPG changes. What you're describing is equivalent to it dropping to 52mpg, but when I switched from 0w-20 to 0w-30 I saw no measurable change. Oil viscosity alone doesn't make that much difference.
 
Originally Posted By: racin4ds

Long story short I went from an average of 36-37mpg using the same fuel stations, same exact trip on my daily commute (~85miles) down to 31-32 mpg!! nothing changed but my oil. Is it possible to see that much a drop with just an oil change?


Absolutely, if the 0W-20 is not lubricating the engine properly which it probably isn't.

You had it right the first time with 5W-30.
 
What I believe the OP is seeing is that gas stations are now selling that stupid winter blend gas.

At operating temperature the 0W-20 is 20W and 5W-30 is 30W.

My question, if the manufacturer calls for 0W-20, then why put 5W-30 in? Makes no sense. The manufacturer uses that viscosity for a reason, not to make people mad.

Put whatever viscosity the manufacturer calls for especially in a new car.
 
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