Gas mileage is one of the issues that really interests me. I would like to
think that with correct engine, final drive set and lowering of the coach
weight, I can get 13-14 mpg. I was quite surprised by Tom's mpg given the
weight of his coach (which is stock and a 455, yes?). I visited a GMC
friend this past weekend who installed a computerized monitoring device
with a flow meter about five years ago. He has a fairly standard 26 foot
Royale with a 403 engine which he has had balanced and blueprinted when it
was rebuilt. On a recent trip down the I-5 from Vancouver to California he
averaged 13-14 mpg. This is a fairly level route with a couple of passes. I
was skeptical but he was very clear that his flow meter was correctly
calibrated (he's an electrical engineer). He also traveled with a friend in
another 403 engined Royale who was down in the 10-11 mpg range. He was very
clear that he put far less gas in his GMC when they stopped to refuel.
(Please note that these are US gallon measurements, not Imperial - which
for you non-Canadian readers is 5 US quarts to the gallon). My friend
maintains that he gets this kind of mileage because he balanced and
blueprinted the engine, had his distributor properly curved and he uses the
cruise control as much as possible (set around 65 mph). I have noticed that
a number of 403 owners will tell you that they get 11-12 mpg. Perhaps like
Tom's coach, a number of our speedometers are registering too low, which
may account for the low mpg.
Vic Marks
Vancouver, BC
75 transmode
think that with correct engine, final drive set and lowering of the coach
weight, I can get 13-14 mpg. I was quite surprised by Tom's mpg given the
weight of his coach (which is stock and a 455, yes?). I visited a GMC
friend this past weekend who installed a computerized monitoring device
with a flow meter about five years ago. He has a fairly standard 26 foot
Royale with a 403 engine which he has had balanced and blueprinted when it
was rebuilt. On a recent trip down the I-5 from Vancouver to California he
averaged 13-14 mpg. This is a fairly level route with a couple of passes. I
was skeptical but he was very clear that his flow meter was correctly
calibrated (he's an electrical engineer). He also traveled with a friend in
another 403 engined Royale who was down in the 10-11 mpg range. He was very
clear that he put far less gas in his GMC when they stopped to refuel.
(Please note that these are US gallon measurements, not Imperial - which
for you non-Canadian readers is 5 US quarts to the gallon). My friend
maintains that he gets this kind of mileage because he balanced and
blueprinted the engine, had his distributor properly curved and he uses the
cruise control as much as possible (set around 65 mph). I have noticed that
a number of 403 owners will tell you that they get 11-12 mpg. Perhaps like
Tom's coach, a number of our speedometers are registering too low, which
may account for the low mpg.
Vic Marks
Vancouver, BC
75 transmode
