Here’s the latest reader question, along with my reply!
Nicholas asks: I read with interest your articles about the mileage of the (current) Chevy Tahoe. I’m a big fan of Chevy generally. I just bought a 96 Tahoe with 75,000 miles, almost 100 percent compression on all cylinders. She runs super clean and I just cruise gently on the gas pedal. Do you know of a way to improve the fuel efficiency of these vehicles? I’m only averaging 12.5 mpg, highway driving and here in NZ gas is $2.29 per litre and rising. Any help would be very much appreciated!
My reply: If you’re only averaging 12.5 MPG on the highway, I suspect your Tahoe isn’t running optimally. It may need a tuneup. It might have a restriction in the exhaust (it is almost 20 years old) or the driveline.
So, the very first thing I would do is go over . . . everything. Compression is one thing. How are the plugs and plug wires? Is the rest of the ignition system working properly? Is the fuel system clean and working properly? Have you cleaned the throttle body (IIRC, your Tahoe has TBI rather than PFI) and checked the fuel filter?
I would check – and probably replace – all fluids. Not just engine oil. Also the gear lube in the rear axle, the transmission/transfer case fluid, too. Use premium synthetics, which flow better, reducing friction. Check all wheel bearings.
What kind of tires are you running? If your Tahoe is shoed with knobby, M/S-type tires that would account for the horrendous mileage. Switch to street radials.
Is it jacked up? If it is, un-jack it.
I’d also check the rear axle ratio. If it’s higher than about 3.08 I’d consider changing out the ring and pinion to something around 3.08 or even 2.73 or so. The truck won’t pull as hard from a standstill, but the V8 has plenty of power and torque to move it adequately and once rolling, the lower gear ratio should noticeably reduce your over the road fuel consumption.
Got a question about cars – or anything else? Click on the “ask Eric” link and send ’em in!
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