Synthetic Scam?

Interestingly, not all weights of all brands of synthetics carry the "Energy Conserving" or "Energy Conserving II" endorsements across the bottom of the API-grade starburst... and some of the dinosaur squeezin's do! To take one specific example, according to the Mobil

Oil is complicated stuff in both its composition and its performance parameters and you can't always optimize everything simultaneously. The energy-conservation rating seems to come from some combination of friction modifiers and viscosity range.

Though I couldn't get it straight from the horse's mouth on the API site, I've seen references to 1.5% and 2.7% fuel economy increase, on some reference engine and set of conditions, for Energy Conserving I and II motor oils, respectively, compared to some oil that doesn't carry that rating.

Those are apparently supposed to be interpreted as long-term averages across a fleet. Many factors affect the fuel economy of an individual vehicle to that extent or even more, especially in the short term, so one has to exercise some experimental rigor and gather a good amount of data before concluding that one oil gives better fuel economy than another on a particular vehicle. However, one's initial hypothesis would be that -- all else being equal -- a motor oil rated as energy conserving would give slightly better gas mileage.

Since this seems to have happened more or less at a change of seasons, you also have to consider some things that others have noted: whether your area switched to oxygenated fuel, whether your engine takes longer to warm up, whether you're carrying more stuff, whether traffic's gotten thicker, whether you're using the car on short errands for which you might have walked or ridden a bike in nicer weather...

So aside from the big hairy problem of controlling all those variables, it really comes down to just what the mechanic put in your car this time. He may well have used a synthetic oil that (while probably very very good in some important areas of this complicated performance space) might not have quite the energy-saving qualities of the previous one.

I'd say, over the course of the coming year do two more changes -- once to your previous oil and once to what you're now running -- and keep tabs on mileage. Right now the data set might be too small, and beset with too many confounds, to have confidence in concluding that the motor oil is having a big effect on your gas mileage.

Cheers,

--Joe

$15 or less. I figure 5 quarts at $3/qt. I'm sure that a manufacturer buying in bulk could get the price lower than that.

$15 at most, probably less.

Just how much lubrication related service do dealers provide? I'm sure they get more money from other wear items than from lubrication related ones.

Longer lasting light bulbs use more electricity for their amount of light put out. So over the life of the bulb, it costs more to use one.

It's much easier to just phase out your gas guzzlers and increase the more fuel efficient vehicles.

If profit margins are the same, it pays to sell a more expensive product. So synthetic would be more profitable.

------------ alex

Where are you getting 3 mpg per vehicle? I tried synthetic for 50k miles in my '97 Expedition and the difference in mileage was negligible compared to conventional oil of the same viscosity.

Ed

Your difference in mileage was less than the tolerance for gas pumps. Legal specs about plus or minus .5%, gas company specs *typically* about .1%.

Steve Triangle Pump Service Ottawa, ON.

Steve, Were you replying to me or Alex. Negligible covers 0.5%. A difference of 3 mpg is not explained by a 0.5% error.

Ed

Sorry for any confusion. Some one stated gas mileage figures to two decimal places. Given gas pump accuracy, that's not repeatable outside of a lab.