Would gas additives help so much so soon?

Dear Bob: My wife and I drove from Mechanicsburg, Pa., to Wisconsin in September of this year, using various 87-octane gasolines. On the last gas fill-up, we used a major-brand oil company’s 87-octane gasoline, which according to you has more of various additives than do cheaper, off-brand gasolines.

We checked gas mileage on each fill-up. Until the last fill-up with a major-brand gasoline, we were getting 34 to 36 mpg. On the last fill-up we got 40 mpg!

Would the extra additives in the major brand make this much difference so fast?

Thanks,

— J.B., Mechanicsburg, Pa.

A: Depending on the quality of the previous gasolines you were using, the major brand could indeed have made that much difference that fast.

Of course, weather conditions might also have played a role, especially headwinds vs. tailwinds. But quality gasolines with complete additive packages will increase overall fuel economy compared to ones that skimp on their additive packages — that’s why people are willing to pay more for a more substantial additive package.

Dear Bob: Wow! You should see what my spell checker did when I typed in your name!

But to business: My 1999 Mercury Cougar V-6 has a low-coolant indicator on the dash. It goes on and off at will, and a “parts changer” garage replaced it to no avail. Several Ford dealers all have had different “ideas/guesses,” nothing I had faith in.

I bet that my indicator isn’t the first one to go bananas, and I’ve heard of a Pontiac’s that acted up and was cured by disconnecting it. Do you have any thoughts on this malady, or should I simply disconnect it and live dangerously?

Thanks for your time, but more so for your entertaining and enlightening articles.

Sincerely,

— J.C., Rensselaer, N.Y.

A: You didn’t say whether the “parts changer” shop changed the light itself or the sensor that actually monitors the coolant level. It may that it’s the sensor that needs replacing, while the light itself is OK. Nor did you say whether the coolant is actually low when the light comes on. If not, it’s almost certainly the sensor itself that is defective.

But to answer your question: Sure, you can disconnect the low-coolant indicator if you wish, especially if you are not in fact losing coolant. There are plenty of vehicles out there that don’t have coolant-level monitors, and they survive very well.

Dear Bob: Enclosed is an article from AAA Hudson Valley’s magazine, Going Places. I’ve highlighted a section that seems to suggest that, the higher the viscosity of your oil, the higher your miles per gallon.

I thought I remembered reading a column in which you mentioned that most manufacturers are actually using or recommending a lower viscosity, such as 5W, to increase gas mileage.

Sincerely,

— D.W., Delmar, N.Y.

A: The highlighted section reads: “Oil viscosity will affect your fuel economy by 1 to 2 percent. And that’s only if you’re using 10W-30 instead of the 5W-30 recommended by the manufacturer. When you switch to 10W-40, the effect is greater.”

I can see why you’re confused, because the piece isn’t written as clearly as it might be.

But I believe that the writer means that using 10W-30 instead of 5W-30 — the oil that, as you and the writer both say, is recommended by most manufacturers to boost gas mileage — will decrease your fuel economy to the tune of 1 to 2 percent, and that using a 10W-40 oil would decrease it even more. That is to say, he is talking about a negative effect on your fuel efficiency.

When the writer says that oil viscosity will affect your fuel economy by 1 to 2 percent, in short, he means you’ll get 1 to 2 percent fewer mpg with a thicker oil.

AMERICAN DRIVERS FIGHT BACK

Here’s a tip that will help you get better gas mileage while fighting terrorism and cutting our nation’s dependence on Mideastern oil:

When motor oil, transmission fluid, trans-axle fluid and rear-axle fluid get old, they accumulate a great deal of dirt, condensation, unburned gasoline, gasoline byproducts and other particulate matter. This increases the overall viscosity of the fluids and requires the vehicle to use more power to run the various units because the gears must work in thicker, dirty fluids.

This is especially true during cold weather, in which high-viscosity, contaminated lubricants get even thicker and more honey-like because their already-thickened condition is exacerbated by the cold.

Change these fluids at the manufacturer’s suggested change intervals, and the units will work in clean, correct-viscosity fluids instead of thick, dirty, abrasive and contaminated ones. You will add life to the mechanical parts and increase fuel economy because the gears, cranks, pistons and other moving parts will work ever so much more efficiently.