Unleaded vs. Premium gas, does it make a differnce?

The old cars ran on leaded fuel and had much higher compression. They benefited the most from higher octane. Some guys would go to the airport to get AV gas for making fast runs.

Partly due to the emergence of air quality standards and the Clean Air Act, cars in the US were detuned in the the 1970s to reduce emissions and increase mileage. Now they don't benefit from higher octane fuel as much as they used to. One of the main impacts of tuners is to advance the timing, which oftenn increases performance and mileage at the expense of increased emissions.

noteven wrote:
Somewheres I remember engines making more power on ethanol (alcohol) than gasoline... oh ya at the drag strip...

An engine has to be capable of making use of higher octane fuels by developing more torque burning them. The fuel itself does not “make power”.

Yes, you can get more power, but you need to squirt a whole lot more in there to do it.

Somewheres I remember engines making more power on ethanol (alcohol) than gasoline... oh ya at the drag strip...

An engine has to be capable of making use of higher octane fuels by developing more torque burning them. The fuel itself does not “make power”.

OP is gone.

Actually it makes maximum horsepower at 5,000 RPM.

At 1800 rpm you make about 140 hp not the rated 350+ hp at 5000 rpm.

That may be true. Not disputing your numbers, but ours turns about 1800 / 2000 on flats overpasses / rolling hills. Just went over two high bridges in Jax Fl in tow haul mode and on cruise, 62 mph. Tach went to 3000-3200 area, stayed @ speed.

Never seen tach over 3200 unless we are caught on an on ramp and have to kick it, but also never been in big mountains. Can't see it getting anywhere near 5000. Must be the tranny / tow haul working.

if it makes you happy, what difference does it make?

STBRetired wrote:
Only place I notice any difference in the MH with running premium fuel os the pocketbook. Don't think the 1999 computer is smart enough to adjust the timing.

The 1999 engine computer is entirely smart enough to adjust the spark timing; that's a pretty basic function of any engine computer unit, and can be accomplished satisfactorily without needing a lot of computer power. The first computer controlled ignition systems were introduced in the 1970s, and by the mid to late 1980s were pretty much ubiquitous. (There were some non-digital-computer-controlled electronic ignition systems in the mix for awhile, too.)

On my old TV, it would knock when towing through hills of Kentucky and Tennessee and through the Smokey Mountains so I used premium. No problem in "flat" states.

BarabooBob wrote:
I also drive a 3.5 EB and when we are in low octane states, I will always pay for at least 87 octane. I do it because the owners manual says to run at least 87. At high elevation most regular gas is 85 octane because a not turbo engine can't use the higher octane. My turbo does not care is I am at sea level or 11,000 ft, it always thinks it is at sea level because the engine just kicks up the boost to make up the difference. That is why my little 3.5 turbo can run comfortably going up the steep grades at high elevation. And contrary to popular opinion, I do not have to wind the engine up. It makes full HP and torque from about 1800 rpms unlike some engines that have to be run at 4000 plus roms to get power and torque.

At 1800 rpm you make about 140 hp not the rated 350+ hp at 5000 rpm.

I filled up in SC with ethanol free premium before going into the mountains of NC. The truck seemed to be running better through the mountains.