Can I get better motor home MPG?
Question:
I recently purchased a 1988 Airstream 325. It has no electronics on the engine except the GM HEI (High Energy Ignition) distributor. It has a Quadrajet carburetor on a GM 454 cid engine.
The vehicle gets about 7 mpg! Is there any room for improving the fuel economy? Are there any adjustments that can be made to the carburetor? Are there any fuel additives that I can use to improve the mileage? Or is there a modern replacement carburetor that could improve the fuel mileage?
I’ve looked into aftermarket throttle body fuel injection systems, but I’m not sure if they would improve fuel mileage. In other words, is there ANYTHING I can do to improve the vehicle’s fuel mileage? I have the ignition timing advanced as far as I can without causing any detonation on hills when I put my right foot to the floor. I drive the vehicle as conservatively as I can, and still I can manage maybe 7.5 mpg at best. I use 89 octane fuel, as recommended, or sometimes premium fuel. I use synthetic oil in the crankcase. I’ve been told toluene and acetone mixed with the gas may clean the carburetor and may improve mileage, but I haven’t tried this. Any suggestions?
Answer:
Some of the main factors that influence your fuel economy are the vehicle’s aerodynamic characteristics, its weight, the efficiency of its engine and drive train, and your driving habits. From a practical standpoint, there is very little you can do about your Airstream’s aerodynamic inefficiencies or its mass. You can moderate your driving habits to increase fuel economy. Install an engine manifold vacuum gauge in your dash and keep an eye on it as you drive, applying throttle in ways that maximizes the vacuum reading.
As far as the engine is concerned, cleaning the carburetor is not going to make a discernible difference in your fuel mileage. A “modern replacement carburetor” is not going to do much for you either. In contrast, however, installing a modern computer-controlled electronic fuel injection system in place of the carburetor will likely yield a noticeable improvement in fuel economy. Even so, you’re never going to get more than about 10or11mpgonthebestofdaysandthe only way around that is to trade your Airstream in for a new, diesel-powered motor home.
