MPG loss in heavier oil - this much?

[poiuy223]

i have about 6600 miles now and on my 3rd OC.
@ 1000, i got rid of the FF and put in M1 5w30
@ 3000, i got rid of the M1 5w30 and put in PU 5w30
@ 6500, i got rid of the PU 5w30 and put in M1 0w-40

go ahead, flame me for wasting oil. i prefer to keep my car clean and the PU cleaned the engine like crazy! i peeked under the oil cap and everything was shiny. plus, i was trying to "rinse" out all the little leftovers in the engine.

with the PU 5w30, i averaged about 27mpg (car computer estimate shown). after 2 days of using 0w-40, the mpg displayed on the screen shows 22mpg, after filling a fresh tank of gas. can going heavier (even though 0w-40 is considered a light 40) cause this much of a difference? if it REALLY is 5mpg that im losing, that means im losing over 100 miles per tank!

 

[cp3]

This is your third change, on a new to you car, correct? If it's a new car with 6600 miles, I would hope it's shiny!!

As for the mileage, 5 mpg seems a bit much to be just from oil. What kind of vehicle are we talking about here?

 

[CATERHAM]

The answer is no.
You're losing about 4% in fuel economy switching from the 5w30's you were using to the M1 0W-40.

BTW what was the daft reason (no offence) in switching from the FF 5w30 to the 40wt oil?

 

[subiedriver]

I went from M1 5w30 HM to 0w-40 in my Subie, filled it up last night, I got 29 mpg with the 5w30 and guess what, I got 29 mpg with the 0w-40. The car definitely runs smoother on the 0w-40, its noticeable.

 

[Mr Nice]

What kind of car do you have ?

 

[cp3]

Originally Posted By: cp3
This is your third change, on a new to you car, correct? If it's a new car with 6600 miles, I would hope it's shiny!!

As for the mileage, 5 mpg seems a bit much to be just from oil. What kind of vehicle are we talking about here?

....oops, missed the FF

 

[aquariuscsm]

I`d say no. I get the same mileage whether I`m using 10W30 or 20W50.

 

[Bluestream]

Ford has determined that going from 5W30 to 5W20 saves .6% in fuel economy

 

[1999nick]

How could the PU have possibly done any substantial amount of cleaning in a new engine that has already had the FF changed at 1000 miles and the M1 5w30 changed at 3,000 miles? It should have looked clean and shiny if the FF was still in there at 6500 miles.

 

[beast3300]

It is possible to loose some mpgs I guess. I haven't noticed any difference from PU 5w30 to my current fill of 4 qts 5w40 T6 (and .5 qts T5 10w30.) Every car is different.

 

[spasm3]

The only way you can check fuel mileage accurately is by averaging several tanks. The car display is not going to be accurate enough. i would average about 4 tanks on each oil before drawing a conclusion. Slight variations in route, driving habits etc make the computer not reliable or just on take a good measure of your mpg.

 

[Ashtray77]

Last I heard, you're supposed to leave the factory fill in for the first normal oci, or did automakers do away with the break in lube and stuff?

 

[demarpaint]

What car, what engine, and what oil does the engine call for?

 

[mongo161]

Did you keep the same filter on the car since the factory fill or did you change the filter out each time. You could have tried a FilterMag wrapped around the oil filter. The FilterMag would have caught any loose particles of Iron or Steel as it entered the filter. The filter should be good for awhile.

 

[poiuy223]

Sorry. Car is a 2011 hyundai sonata turbo. Switched to a 40wt cuz manual recommends 40 for max performance. I switched oil filters every time. I'll see how it goes after a week

 

[Arnaldo]

The trend by automotive engineers seems towards lower viscosity oils, 'cause they not only improve gas mileage, but also help dissipate engine heat better, therefore keeping moving parts in better shape longer. Heavier viscosity, contrary to popular belief or logic, doesn't "protect" moving parts better at all.

With all the additives they put in modern oils, lower viscosity is here to stay, I guess. Greetings, dudes.
____________________________
Flawless '04 350Z Touring Coupe

 

[tonycarguy]

There's no chance that switching to a 40wt oil could have caused a 20% reduction in F/E. That would also imply a noticeable reduction in horsepower too. You would have felt it. The difference is obviously because your driving patterns changed or it was windier that day or whatever

 

[whip]

Originally Posted By: poiuy223

go ahead, flame me for wasting oil. i prefer to keep my car clean and the PU cleaned the engine like crazy! i peeked under the oil cap and everything was shiny. plus, i was trying to "rinse" out all the little leftovers in the engine.


What did it "clean like crazy"?

 

[Familyguy]

It makes a difference, but I suspect it's less than 1%. There's some other cause for your mileage drop.

 

[JZiggy]

Originally Posted By: Familyguy
There's some other cause for your mileage drop.


Rings not sealing because the oil's too clean?