Mobil Drive Clean = Decreased MPG

[Ray H]

I can't fathom that one brand of 10w30 motor oil would vary in fuel mileage THAT much over any other brand of 10w30 motor oil - especially considering that Mobil Drive Clean is the factory fill oil in Hondas, as it is also Honda branded motor oil at the parts counter. It could have been a bad load of gas, you know - or even something more sinister. I remember the fuel mileage on my '96 Accord took what seamed to be a five mpg dump with gas from a particular station. The next time I filled up at that station, I was amazed to find that my Accord's 17.04 gallon tank took 24 gallons to fill. (On the previous fillup, my tank was only down halfway so I hadn't noticed the descrepency.) I contacted the County's bureau of weights and measures and registered a complaint. For the next six months that particular pump had a posted price 15 cents/gallon cheaper than the rest of the regular grade pumps. People avoided it like the plague. I didn't. Contrary to what I'm certain other customers suspected (and may have been told by station personnel) there was nothing at all wrong with the gasoline from that pump (hey, it all comes from the same common "regular" underground tank!). I realized right off that the one pump's price reduction was at least partly the station's penalty for jacking the flow delivery display up or fellow "sting-ees" thought the pump was still optomistic in its flow delivery. Oh, and the flow display was spot on as nearly as I could tell after that complaint initiating episode, too.

[ September 24, 2004, 01:12 PM: Message edited by: Ray H ]

 

[brianl703]

I've also heard about some pumps which are programmed to cheat unless they have 5 or 10 gallons withdrawn from them. Not coincidentally, the weights and measures department uses a 5 or 10 gallon flask to verify that the pump is accurate.

Maybe I should add gas to my car in 10 gallon increments and see if my fuel economy seems to be going up??

 

[eljefino]

^ what he said, I have also heard.

 

[blupupher]

Well the first tank of gas I had used super, I normaly use regular, so I first thought of the gas thing also. But it has now been 1500 miles (4 tanks of gas, all from different stations, heck, even different states), and the mileage is still down the 2-3 mpg. The only difference I can think of is the oil. And yes, it is still a new engine and not totaly broken in yet, bet every other new vehicle I have ever had, the mpg has slowly gotten better over time, not dropped all the sudden. I guess I really can't complain, It went from 33mpg to 30mpg.
Like I said above, I don't plan on using this type of oil again, was just curious if any others had a similar situation other than the one I linked to above.

 

[gimpy]

Really sounds more like a knocked loose vacuum hose, dragging brake, fouled/missing plug. Not arguing with you just don't believe any oil is capable of causing that kind of mileage difference.- Mobil would be bankrupt. Alot of other people would have noticed this.

 

[Ray H]

You don't suppose your dealer's oil change monkeys overfilled the sump do you? (The oil change brainiacs are at the bottom of the food chain and are in training to graduate to pushing brooms and washing cars just off the truck...) There've been posts about exactly this sort of thing happening - and the incidents aren't restricted to Hyundais, either. I have such a distrust for routine dealer servicing that I never bothered with my Sonata's first "free" oil change. Most volume oil change places meter bulk oil out of a drum, but the metering precision is as apt to be off as on (assuming the brainiac set the delivery volume correctly) - in some cases over a quart high. If significantly overfilled, the crank counterweights could be splashing into the oil. Overcoming the parasitic hydraulic losses to maintain engine rpms might well affect fuel mileage adversely. No doubt something's going on here, but the question is what.

 

[farang]

why not just drain it (assume that you get more than 2000mi), refill with your "favorate"? Problems solved (but may be not)!

 

[gimpy]

You don't suppose your dealer's oil change monkeys overfilled the sump do you? (The oil change brainiacs are at the bottom of the food chain and are in training to graduate to pushing brooms and washing cars just off the truck...) There've been posts about exactly this sort of thing happening - and the incidents aren't restricted to Hyundais, either. I have such a distrust for routine dealer servicing that I never bothered with my Sonata's first "free" oil change. Exactly what happened to wife's new caravan. Dealer knocked off accessory vacuum hose nipple. It was brand new and running like crap for 3 weeks (she didn't notice it!

) I have alot of vacuum hoses near my oil fill cap. That's where my post came from. Probably more human than oil problem.

 

[blupupher]

No oil over-fill, checked that 2x already since the change. I did not notice anything knocked loose, but did not look real close. I will take a closer look in the morning and see if there is anything though. There really are not any hoses and such around where the oil fill, drain, or filter are though. I guess anything is possible.

farang, I have thought of that also. It was initialy my plan to drain this fill @ 5000 miles, but I had decided to wait another 1000 to get 3000 out of it, but if I can't find any other cause for the decrease in mpg, I already have the M1 and filter in the garage. Heck, I am kinda curious as to what a UOA on this stuff might be like. Not curious enough to spend the $20 on though.

I also think I am going to go talk to the service rep about this and see exactly what they put into it.

 

[blupupher]

Well, I just had my free 3000 mile oil change from the dealer last week, and they used Mobil Drive Clean 10w30. Since that time I have noticed about a 2-3 mpg drop from what I normaly get. Same route and driving conditions. I only found 1 other post that mentions this, anyone else?
FWIW, it is a 2004 Hyundai Elantra 2.0 4 cyl auto, 4500 miles, 1st oil change done @ 1000 miles with 2 qts Penzoil 10w30, 1 qt Penzoil 5w30, and 1 qt Pro-Line 10w30 (SJ rated oil, it's what I had sitting in the garage), no change in mileage till the Mobil DC was put in. Could it have anything to do with the 1 qt of 5w30 that was mixed in? I would not think it would make that much of a difference.
I am going to go M1 10w30 @ 6000 miles with approx 7500 mile OCI and hopefully the mpg will come up. Just curious if anyone else has noticed this with the Mobil DC.

 

[haley10]

Since your engine is new and still breaking in, I wouldn't put much significance in the mileage numbers.

It will plane out and you are sure to get good mileage with the Mobil 1.

 

[Blue99]

Here is a good reference article for gas mileage factors at my favorite Chevron technical site.

Chevron Gasoline Facts

Take a look at Figure 2.

Of the available energy in a gallon of gasoline:

16% lost to engine mechanical
10% lost to drive train mechanical
12% energy transmitted to the wheels

So the motor oil is affecting only a potential 16% of your gas mileage mpg.

Also, an additional motor oil & mpg statement:

Here is one author's estimates of the impact of engine friction on fuel economy.

Up to 28 percent increase in fuel economy, if engine friction were completely eliminated (not possible).
Up to 5.8 percent increase in fuel economy for real driving cycles, if an improved motor oil reduced engine friction 50 percent.

So a 2-3 mpg drop in your gas mileage solely due to running a slightly higher viscosity probably is not mathematically possible.

Check out the Chevron chart listing the many factors that affect a vehicle's mpg!

 

[Big Jim]

I used Mobil Drive Clean 5W30 nearly exclusively for 190,000 miles on my 98 Contour SVT. When I have used other oils, I have not noticed a difference in fuel consumption. I check fuel consumption at nearly every fill up. I recently switched to Mobil 1 and extended the oil change interval from 3,000 miles to 5,000 miles. There is still no difference in fuel consumption. The significant thing from the change though is that I need to add oil at about 3500 miles, so I'm thinking of going back to the old routine.

So, no, I don't think the Mobil Drive Clean is responsible for your drop in fuel economy.

It is more likely to be due to changes in driving routine, seasonal variation in fuel, weather changes, or any of a myriad of things.

 

[blupupher]

Well, nothing under the hood was out of place, and it was Mobil DC 10w30 put in there. My front tires were both a bit low (27 and 28 psi), the rears were fine. Mileage has come back to almost the same, so I guess it was in part due to the low tire pressure (talked to the service rep about that one, he had no answer why the lowered the pressure, I'm guessing the checked and adjusted the rears, but not the fronts), not the oil. I will see if there is any improvement when I go to M1.