Do EPA Economy Ratings Rely
On Ethanol-Gasoline Fuel?

Q: Do the mileage figures printed on new car stickers reflect use of ethanol-blended gasoline, the only fuel now available for most or all consumers, or whether the sticker mileage claims are based on using 100% gasoline. If the latter, does the government intend to mandate the use of gasohol to create more realistic mileage numbers?
-- W. Hayes,
Dover, Mass.

Associated Press

The EPA ratings on vehicles like this Toyota Prius are based on ethanol-free fuel

A: The fuel-economy ratings on new-car window stickers are calculated using pure or "straight" gasoline, not the commonly used 10%-ethanol blend called E10. I can't recall the last time I filled up using gasoline that wasn't blended in this way.

Fuel economy decreases by about 2% for vehicles running on E10, so a car rated at 25 miles per gallon will actually travel about 24.5 miles. Of course, the negative effect of blended fuel is tiny compared with the effects of changing one's driving style and keeping the car in top shape. Still, a loss is a loss. While E10, and E15, and may reduce overall oil consumption, it isn't helping individual vehicle fuel economy.

Q: During one of the gas "crises" of the past, the federal government mandated a 55-mile-per-hour maximum speed limit on local and interstates alike. Is this being considered now? If not, why not?
-- Bill Francis,
Grinnell, Iowa

A: Yes, a few politicians are talking openly about conservation, possibly thought lowering speed limits. Earlier this month Sen. John Warner (R., Va.) sent an open letter asking the energy secretary and the Government Accountability Office to study the possible benefits of lower speed limits. (Related article) This wouldn't necessarily result in a limit of 55 mph like the one we lived with from the mid-1970s to the mid-1990s. But it's easy to imagine future speed limits being lower than today's.

According to the Environmental Protection Agency, fuel economy generally declines at speeds above 60 mph. Having found this to be accurate anecdotally, I can picture a 60 mph national speed limit within the next several years. And even though the limit makes sense, I predict strong resistance from drivers who have come to appreciate higher speed limits for their time-saving potential. For me, the jump in speed limits to 65 mph on long stretches between New York and Boston helped cut an hour off that drive. The same trip seemed interminable at 55 mph.

Q: I drive a BMW 335i with a six-speed manual transmission. A recent review of the car stated that the engine is just as "happy" in sixth gear going under 40 mph below 2000 rpm as it would be driving in fourth gear at a higher rpm. I had always learned that higher gears at lower speeds causes engine lugging and underperformance. Is it correct to presume that mileage will improve by driving at lower engine speed? I have already seen that performance doesn't suffer at all.
-- Paul Joseph,
Shaker Heights, Ohio

A: I think you're right about the lugging. The 335i's engine has a lot of low-speed power or torque, which allows it to accelerate the car smoothly even from very low engine speeds in a high gear. However, I don't think the engine is actually "happy" when accelerating from less than 40 mph in sixth gear. It's more like a friend who remains a good sport even when put upon. The friend might agree to help you move to a new apartment, but he'll also wish you hadn't asked.

Cruising slowly through town in high gear can minimize engine speed and, in some cases, save gas. But acceleration will be weak if the engine is out if its most efficient speed range in a too-low gear.

Q: I recently was provided information about an entity called Fuel Freedom International. One product offered is a tablet called MPG-caps. These caplets are supposed to increase gas mileage 7% to 14%. I am skeptical. If these products really work as claimed wouldn't billions of them be sold now? Any opinion regarding these products?
-- Eric Steger,
Seminole, Okla.

A: Your skepticism is well founded. Most simple fixes that claim to improve fuel economy are based on theories that are shaky at best. Studies by the EPA and Federal Trade Commission have found the broad range of products that claim to save gas simply don't work. While the studies might not have looked at MPG-caps specifically, I still doubt that tablets will work as advertised in real-world driving.

Aftermarket parts such as intake and exhaust systems can improve an engine's efficiency, but the ones that work are costly and specially designed for specific vehicles.

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