Chris wrote;
>could I get the run down on what type of gas is best used for the 455.
87 octane unleaded
>
>I know that in 1976 leaded gas was readily available and run significantly
>higher octance than what is available today in regular unleaded.
Regular leaded fuels usually were also 87 octane by current standards, 87
octane on the pump is a Research Octane Number (RON) of 91. No GM Passenger
car engine ever was designed to require and fuel of higher octane than a RON
of 98, which coresponds to a pump number of ~93 now. Incidentally, since
circa 1972, it has been illegal for manufacturers to sell a vehicle in the
USA that doesn't operate correctly and perfectly on 87 Unleaded. Thats the
LAW. Frequently owners manuals recommend high test fuels, but they cant
REQUIRE it. Naturally, a manufacturer would rather you bought so-called
premium fuels at your own expense rather than darkening a service department
asking for timing adjustment or repair.
>
>Someone told me that burning premium (higher octane) in the GMC would
result
>in a better running engine and better gas mileage, enough to offset the
>additional cost. Any truth to this claim.
No.
Unleaded fuels are perfectly safe and adequate. Don't buy the valve seat
wear stuff either- they wear the same rate under the same circumstances with
or without lead. #1 killer of them is high temperatures (Wide Open Throttle)
in tandem with very high engine speeds (over 3800 RPM or so) as the high
temp softens the materials, and the high speeds permit pounding damage.
The engine should and can run perfectly anywhere you are ever going to drive
on 87 Unleaded, use that- if theres a problem in drivability or tuning, find
the cause, its a better deal than attempting to mask it by increasing your
fuel costs 25%.
Hope this is reassuring
Brent
>could I get the run down on what type of gas is best used for the 455.
87 octane unleaded
>
>I know that in 1976 leaded gas was readily available and run significantly
>higher octance than what is available today in regular unleaded.
Regular leaded fuels usually were also 87 octane by current standards, 87
octane on the pump is a Research Octane Number (RON) of 91. No GM Passenger
car engine ever was designed to require and fuel of higher octane than a RON
of 98, which coresponds to a pump number of ~93 now. Incidentally, since
circa 1972, it has been illegal for manufacturers to sell a vehicle in the
USA that doesn't operate correctly and perfectly on 87 Unleaded. Thats the
LAW. Frequently owners manuals recommend high test fuels, but they cant
REQUIRE it. Naturally, a manufacturer would rather you bought so-called
premium fuels at your own expense rather than darkening a service department
asking for timing adjustment or repair.
>
>Someone told me that burning premium (higher octane) in the GMC would
result
>in a better running engine and better gas mileage, enough to offset the
>additional cost. Any truth to this claim.
No.
Unleaded fuels are perfectly safe and adequate. Don't buy the valve seat
wear stuff either- they wear the same rate under the same circumstances with
or without lead. #1 killer of them is high temperatures (Wide Open Throttle)
in tandem with very high engine speeds (over 3800 RPM or so) as the high
temp softens the materials, and the high speeds permit pounding damage.
The engine should and can run perfectly anywhere you are ever going to drive
on 87 Unleaded, use that- if theres a problem in drivability or tuning, find
the cause, its a better deal than attempting to mask it by increasing your
fuel costs 25%.
Hope this is reassuring
Brent
