Hey all!
New to the forum, have a question re: our 1988 454 Suburban. This is a CA truck with no rust, transplanted to Indiana about 2 years ago.
The truck is in very good shape, pulls anything we've thrown at her, but my GOD, the gas mileage is awful. I'm not talking 10mpg bad, I'm talking 5mpg!!!! This mileage was verified last weekend on a 400 mile trip to Chicago and back, pulling a 24' Haulmark enclosed trailer 65-70mph. I know of people who get 8mpg with a 454 in a 30' motorhome running the same speed!!!
A little more on the vehicle: 180K miles, new Mark V 454 crate engine installed at 130K. 4.10 gears, TH400 trans(no OD), Hummer H2 wheels 265/65/16 Goodyear Fortera tires and I'd say a 2" body lift. Cruise RPM at 65 is 3100rpm, which is right at the engines power peak.
I've heard about all kinds of people getting 12mpg pulling with 454s and all that stuff, but I don't necessarily buy it. I can't believe however, that this engine is so inefficient that it only gets 5mpg pulling. Surely there is a happy medium here!!! I can't imagine the fuel injectors could possible spray that much fuel in the damned motor!!!lol!! I think that 8mpg would be very reasonable pulling a 24' trailer with a 3300lb car. That would put the cruise range at pretty close to 300 miles(vs. the 200 mile range currently), which is pretty reasonable.
Are there any things that might be contributing to the seemingly excessive consumption, or given the stats, is this about all I can hope for mileage-wise?
As an aside, the truck does have an issue when it's cold outside, it runs very rough and rich, but based on the recommendations from a mechanic, I ran a 't' fitting to the MAP sensor to an additional vacuum source and that seems to have diminished the time it runs rough.
Any and all ideas would be appreciated!
Brian
New to the forum, have a question re: our 1988 454 Suburban. This is a CA truck with no rust, transplanted to Indiana about 2 years ago.
The truck is in very good shape, pulls anything we've thrown at her, but my GOD, the gas mileage is awful. I'm not talking 10mpg bad, I'm talking 5mpg!!!! This mileage was verified last weekend on a 400 mile trip to Chicago and back, pulling a 24' Haulmark enclosed trailer 65-70mph. I know of people who get 8mpg with a 454 in a 30' motorhome running the same speed!!!
A little more on the vehicle: 180K miles, new Mark V 454 crate engine installed at 130K. 4.10 gears, TH400 trans(no OD), Hummer H2 wheels 265/65/16 Goodyear Fortera tires and I'd say a 2" body lift. Cruise RPM at 65 is 3100rpm, which is right at the engines power peak.
I've heard about all kinds of people getting 12mpg pulling with 454s and all that stuff, but I don't necessarily buy it. I can't believe however, that this engine is so inefficient that it only gets 5mpg pulling. Surely there is a happy medium here!!! I can't imagine the fuel injectors could possible spray that much fuel in the damned motor!!!lol!! I think that 8mpg would be very reasonable pulling a 24' trailer with a 3300lb car. That would put the cruise range at pretty close to 300 miles(vs. the 200 mile range currently), which is pretty reasonable.
Are there any things that might be contributing to the seemingly excessive consumption, or given the stats, is this about all I can hope for mileage-wise?
As an aside, the truck does have an issue when it's cold outside, it runs very rough and rich, but based on the recommendations from a mechanic, I ran a 't' fitting to the MAP sensor to an additional vacuum source and that seems to have diminished the time it runs rough.
Any and all ideas would be appreciated!
Brian