Can your oil selection really affect your mpg?

[Ugly3]

I will give you a MPG story.

I just finished a trip from Chicago to Seattle (about 2100 miles one way). 1998 Chrysler T&C 3800 V6, 160,000 miles on the vehicle.

On the trip there we drove 30+ hours straight through. We ran 70 MPH against a horrid head wind in relativly cold temps (20's and 30's at night). The van was loaded pretty good (maybe 1000 pounds). The MPG was 20 for the overall run to Seattle.

On the way home my wife and I drove only in the daytime, we ran 75 MPH most of the way, the wind was relativly tame, and the temps were higher (50's and 60's most of the time). The load was gone. By the time we got home the overall MPG was 22.6 for the 4400 miles trip (we did a little sighseeing on the way back).

This means we must have gotten about 25 MPG on the way home. Differences? Positive (wind, temp, load). Negative (speed).

As for oil, ran Mobil 1 5w30 SS, consumed 3 or 4 ounces on the trip. Would normally consume 1/2 quart in 5,000 miles. There was more than a little high RPM mountain climbing so I am pretty happy with the oil consumption rate.

 

[Jay]

I've heard that you can expect about 1.5% change in mileage from one grade to the next, but I measure much more change than that in my Acura RSX.

I see a full 1mpg difference between M1 5w-30 and M1 0w-20. So the 0w-20 is like getting 7.7 gallons of gas free on a 7k mile interval--or $20 free. There's no wear penalty with the 0w-20; I've proven that again and again.

 

[Norm Olt]

Wow! 1st time I've been nominated for anything, recently... Except for "Who buys the next round?"

Is there a prize? A quart of ARCO Graphite, maybe?

Cheers!

p.s. No, I think the miles driven tax "idea" is still in the planning stage. The additional insurance tax/surcharge (which I don't think they EVER want to let the voters get a crack at) is in the planning stages, too.

After all, this is the State where a 7% increase in school spending is still referred to as a "cut". 'Cause it was "cut down" from the 14% spending increase (following double-digit increases for 5 years in a row) they wanted to implement.

[ April 09, 2005, 08:32 PM: Message edited by: Norm Olt ]

 

[LarryL]

For me one of the biggest problems in getting good gas mileage is the brake pedal. If you can stay off that pedal, you'll get better mileage. There is a problem with staying off the pedal and pacing yourself thru traffic. People will beat you to red lights. By the time you catch up, the light will be green, and you'll just have to keep going. If you can give up winning the stop light grand-prix your mileage will improve. As good as the lightest oil is, habits are better, when it comes to mileage.

 

[JeffD11N]

I did a little playing with an 83 Escort I have for a work car. I freshened the motor a couple of years ago and thought what the heck lets play. I had run 10w-30 Chevron Supreme since the rebuild for about 9000 miles. Averaged about 24 mpg.

I switched over to 5W-30 Torco full Synthetic. Same stuff that guys like Warren Johnson are supposedly running in thier Pro Stock Drag cars.

Not one iota of difference in mpg. I did however notice that it took about an extra mile down the road in the morning, to see the temp gauge do that thermostat just opened plummet.

Ran the Torco for 12,000 miles changing the filter at 4k and 8k. Entire OC stayed at 24 mpg.

When I dumped the Torco I thought lets try Chevron RPM 15W-40 I use in the farm tractors. MPG dropped to 21 and oil psi jumped 5 lbs.

Well now I'm back to 10w-30 Chevron Supreme and puttering along at 24mpg. Just can't justify the cost of synthetic.

Not scientific but realistic.

 

[LarryL]

Warren Johnson used Red Line oil, one of those skinny 5 or 2 weight oils depending on conditions.

http://www.redlineoil.com/motorsports.asp

 

[brianl703]

According to the trip computer, since I replaced the harmonic balancer on the 88 Mustang GT and set the timing to factory spec (it was retarded 10 degrees due to the original balancer slipping), I got 31MPG on a 40-mile trip today. After I arrived at my destination I got stuck in the traffic jam from **** [1], which dropped the average fuel economy to 24MPG. On the 40-mile trip back, the average fuel economy increased to 25.8MPG by the time I got home.

Not bad for a V8.

[1]primarily caused by poor traffic signal timing.
As the light you're at turns green, the next one up just turned red, and so on.

 

[JeffD11N]

Thanks for teling me that Larry.

Torco has a bunch of racing oils and the dealer I got it from is a dragracer. He said he knows Warren and the stickers on the side of the car are not exactly what's in it. I took him at his word, and I will take you at yours.

 

[n8wvi]

Sure, it can have an affect, BUT IN WHICH DIRECTION??? I've had our Impreza wagon for 8 years and 137,000 miles now, and the best mileage I've had during an entire OCI was when I was running Delvac1300 15w-40. First 80k miles was Mobil1 5w-30, next 20k was with Amsoil 5w-30(ASL), then mostly Pennzoil 5w-30. Then last summer, I ran the Delvac 'just for giggles' and got my best mileage ever, tank after tank after tank, for the entire OCI. I also doubt it's because I was getting a better ring seal on a tired engine. Reason I doubt it is, no tired engine in an all-wheel-drive vehicle will yield 33MPG when it was only rated for 29MPG when new. Can I explain my results, no, I can't. Will I likely be running a quality 15w-40 again this summer, yep (Delvac or Delo

I haven't decided yet).

Dave

 

[TooSlick]

Dave,

With all due respect, the issue really isn't up for debate, in fact it's simple fluid mechanics. Stir a glass filled with honey and one filled with water. Which takes more energy to stir at the same rate? This energy also goes directly into heating the heavier oil, since energy can't be created or destroyed.

Pumping and shearing (deforming the oil film between moving parts), a more viscous fluid takes more energy, period. Of course there can be other X factors that influence these results - specifically average trip length, ring/cylinder wear, ambient temps and who is driving the car most of the time. However engine Sequence tests and fleet tests done under tightly controlled conditions and employing very accurate fuel flow meters will always indicate that thinner lubricants reduce energy consumption.

This is why all OTR trucks have gone to low vis synthetics in the HD transmissions and differentials. They used to run a straight 90wt in the transmissions and often an SAE 85w-140 in the diffs. They now run a stright 50 wt/GL-1 rated synthetic transmission fluid and 75w-90 gear lubes.

Run Delvac 1, 15w-40 and Mobil 1, 0w-40 back to back and tell me the 15w-40 gives you the same or better fuel efficiency. Even folks who switch from Mobil 1 to Delvac 1 often report significantly less fuel efficiency.

Ted

 

[n8wvi]

TS, you're right, it's not up for debate, it's a fact that I got better mileage for the entire 6,000 mile OCI on the Delvac1300 than I ever did during the previous 7 years of ownership of the car in which we used various 5w-30 oils (Mobil1, Amsoil AME, and Pennzoil dino). My engine isn't a glass w/ a stir stick either. AGAIN, I'm not saying I can explain it, it's just a fact. An no, I hadn't replaced the spark plugs, air filter, gear lube, tranny lube, fuel filter, or anything else prior to that OCI.

Dave

 

[Dr. T]

I agree...it's not a simple stirring rod in a beaker scenerio. Some oils 'seal' the engine parts better and/or provide better lubricative properties.

For eg. I just tried a round of GC and am getting worse fuel economy than the Belgian 5-40.

 

[ebaker]

API energy conserving oils are supposed to give a 2% increase in fuel mileage. I'd guess you could expect a similar percentage when changing to a thinner more friction modified oil.

 

[MNgopher]

I can only report what I know, and what I've seen is that oil weight can affect fuel mileage in a big way.

How do I know? I'm currently in year three of a three year deal to see if I noticed any difference running a 5w30, a 5w20, and a 5w40 in my '99 F150 with the 4.6l V8. I'm nearly at the end of my 5w40 run, and there is no doubt that I get about 5% lower fuel mileage using 5w40 versus 5w30 or 5w20. With current fuel prices what they are, this isn't a good thing. UOA's suggest marginally better wear numbers using 5w40, but enough for me to care about, no.

And before anyone asks, driving styles were similar, as were overall temps, etc... over each of the 1-year testing periods. Kind of throws out the tank to tank variability...

 

[n8wvi]

That settles it then!

Different vehicles respond differently (big surprise, eh?). But I'm NOT alone in the "thinner doesn't always mean better mileage" crowd.

Dave

 

[Jay]

If the thinner weight oils are truly delivering less gas mileage than the thicker oils as some claim, then the thicker oils must also be producing thinner films than the thinner oils since a fluid's internal resistance to motion is what produces the film in the first place.

 

[bulwnkl]

quote:

---

Originally posted by n8wvi:
TS, you're right, it's not up for debate, it's a fact that I got better mileage for the entire 6,000 mile OCI on the Delvac1300 than I ever did during the previous 7 years of ownership of the car in which we used various 5w-30 oils (Mobil1, Amsoil AME, and Pennzoil dino). My engine isn't a glass w/ a stir stick either. AGAIN, I'm not saying I can explain it, it's just a fact. An no, I hadn't replaced the spark plugs, air filter, gear lube, tranny lube, fuel filter, or anything else prior to that OCI.
Dave

---

Yeah, my '91 Subaru XT6 (AWD MT) also gets better mileage on John Deere Torq-Gard Plus 50 15W40 than on any dino 10W30 I've tried. Just like you, it's not for a tank or so, it's all the time and no other conditions change; it's just a fact.

 

[tenderloin]

Better gas mileage with a 15W-40?

Better contact Ford, Honda and Chrysler. They are missing the boat by going with thinner oil.

They should be using thicker oil

 

[vwoom]

Lately, my gas mileage is off by 2+mpg less now with GC 0w30 compared to the usual 5w40 syns I run in the 1.8T...and the new fill of GC is pretty new at thickest 5w40 I've used.

 

[sdude2k2000]

I'm running M1 EP 5w30 in my new Mazda3 right now (speced for 5w20)... and I haven't noticed a gas mileage difference

All I know is the moronic service guy behind the counter told me "umm... your vehicle is speced for 5w20". Really?

I felt like having a BITOG moment and asking him if he knew what the cST @ 100*C was for the Motorcraft 5w20 that they offer and for the Mobil1 EP I was about to put in the car.