Skip the auto shop - Our mechanics make house calls

Q: Bad gas mileage and always runs in 4WD - 1979 Chevrolet K20 350 V8

asked by on

My truck is all the time running in 4WD and the gas mileage is terrible. I have changed the oil, transmission fluid, filter, and installed duals with turbo mufflers. After all of that, my truck still only averages around 10 mpg. When I first start driving, it is a bit sluggish. I am thinking that I might get manual lock out hubs for the front to take it out of 4WD. Perhaps I will invest in a top-rate filter system like edelbrock. What is your advice for how I can get my truck to perform with better gas mileage?

Hi there, thanks for your question. Yes, these older Chevys do have full time four-wheel drive. There are kits available that will disengage the differential from the transfer case, but I’ve heard mixed reviews on how well they work. You could also convert your full-time NP203 transfer case over to a 205. If you’re doing this solely for mileage, however, I would think twice. Really, 10 miles per gallon isn’t bad for your truck. Converting to part time four-wheel drive might net you a little better mileage, but the time, effort, and cost will probably outweigh the mileage gain. If you think your car should be getting more mileage than it is, consider having one of our certified automotive technicians come to your home or office to diagnose and repair the issue for you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My car makes a grinding noise when shifting to reverse

The first thing to check is the transmission fluid level. If fluid level is okay, then the most likely problem causing a poor reverse engagement is low fluid pressure in the transmission. This could be caused by a worn pressure...

Q: The speedometer, odometer, & mileage gauges are not working.

This is likely related to what is called a speed input/output shaft sensor which is a sensor mounted down on the transmission that monitors the speed of the output shaft of the transmission. This is relayed to your ECU which...

Q: Can't find oil plug

Hello. The drain plug for the oil should be underneath the truck in the oil pan of the engine. There may be a splash shield covering the oil pan. If there is, this will need to be removed to get...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...