use regular in superchaged MOTO

[umina]

Hello all, i'm thinking about buying a 2000 or so Buick regal, either GS or LS. I'd really like to have the GS with the supercharger, but with the price of gas, maybe not. So i've been looking into running the supercharged car on regular gas. I know TONS of people out there are doing this with their GM cars when they lease them cause they give'm back in a few years and who cares, right? So i've got a nagging question as to running normal octane (87) in the superchaged motor.
87 Octane should be fine to use in any car with up to a 9 to 1 compression ratio. So the regular non super charged 3.8 series II has a 9.4 to 1 compression ratio, while the supercharged variant has 8.5 to 1. SOOOO, shouldn't it be OK to run 87 octane in the superchagred motor and let the knock sensor retard timeing to compensate without any engine damage? If not, i'm gettin the LS and savin 20 cents per gallon, but it makes sense right?? Or are my facts way off base, sometimes this old internet lies to me...... :o)

[tman]

Running 93 will get you better performance, however, the computer will compensate for lesser fuel grade, so 87, 89, or 93 is okay, just depends on what you want.

[umina]

Will this cause damage to the motor over the long run though?

[tman]

No worse damage than any engine gets from normal wear and tear, which by the way is supurb with the 3800, I will say thoug, superchargers like to die after about 80000 miles, so plan to replace it's bearings every 80000 miles.

[umina]

Thanks for the Info, I feel better about a GS now......

[georgsant]

I have a 99 Regal GS that I bought 8 months ago and I've been using 87 octane and the previous owner was also. I notice I get normally about 19-20 mpg and drive mostly highway miles. It's rated 18-28 mpg. What can I do to improve the mileage? Will higher octane also improve the mileage or just the performance. I recently changed plugs, fuel filter, air filter, oil filter, oil and SC oil with not much improvement.

Thanks

[agelder]

You will get better mileage with the better gas. I have experienced this quite a bit. If you drive mostly in town, and don't have your engine modded (excludes me) you should be okay with regular, but I'd at least spring for the 89 octane. With the supercharged engine you run the risk of knock before the computer can react and retard the timing if you use 87 octane, which theoretically could wear the engine quicker. If you do a lot of highway driving, I have noticed as much as 3-5 MPG difference on long trips when using premium vs regular. Just remember that EPA figures have NOTHING to do with real world numbers.

And by the way, the superchargers don't die after 80k, the couplers however, do. It's a $40 part (do a search on google for eaton coupler) that's easy to replace. I've had my supercharger for 140k and it's the original blower (with ~40k of those miles with an overdriven supercharger via a 3.4" pulley), but i'm replacing my coupler in a few weeks.