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How to reduce Octane and increase gas mileage

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pshojo

New member
My parents have a 2004 Buick Ultra. They want to get away from having to use 91/93 octane and want to get closer to 30MPG. What can I do to their engine set up to obtain this? Or would i need to do a engine swap with the N/A engine? i have a 04 grandprix that i could swap engines with. I'm not sure if that is the route i want to go. I'd rather help them update their engine tuning or what ever? thoughts?
 


You could get a canned tune set for 87. Get someone to give you a ton of cruise timing as well and you'll be in business.
 
A full tune up and driving under the speed limit should be an easy 28-30 mpg in that thing.

Doing a motor swap and getting it to run correctly would cost you alot more time and money than it's worth.

And in the end, you still will likely not gain much mpgs.


91 octane cost like 5-7 more dollars per fill up, not like it's an arm or a leg here.
 
.30 cent differnce over average 12gal fill up is $3.60
cruise timing is wonderful but with low octane and convertor locked- kr comes if it don't unlock quickly under throttle.
So yeah a good tune with a couple scans should be okay but even stock n/a knock
 
I would look for a 4.0 or 4.2 blower pulley and swap that on. Fill with 87 octane and beat the piss out of it.
 


I did a LOT of driving with my '98 Riv, and would frequently take off the SC belt and use 89 Octane. Helped by about 2 MPG.

Driving technique can go a LONG way too- drive 62MPH instead of 75MPH. Use cruise control. Strategically brake before red lights so that you don't have to come to a full stop. Bump the tire pressure up 2-4 PSI (or maybe more). Take routes favoring right-hand turns instead of left turns (UPS does this). Use the lowest octane that you don't get knock (as long as their driving habits are consistent). In cold weather, block off part of the radiator to get up to temperature more quickly and run a few degrees hotter. Make sure airflow under the car hasn't been distrurbed (i.e. make sure all of the air dams are in place). Wheel alignment. Run the hottest available thermostat. Good plugs, wires, coils. Have the fuel injectors flushed on a bench and flow-tested to ensure uniform flow (and replace any of them that are found to flow improperly). Run a higher viscosity oil (i.e. 5-20 instead of 10-30) if their driving habits will support that.

Oh yeah, and make sure their LIM gasket has already been swapped out, and that the coolant is properly changed out. But that won't really affect gas mileage per se.
 


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