I have a 2002 chev silverado with 100,000 km on it with the 4.8L and auto
trans. I consistantly get an average of 12.5 mpg. I still have original
spark plugs, air filter (filter vacuum gauge is still in green area) fuel
filter etc... The truck runs perfect so I see no need to start changing
things like these and the manual does not say to in there maintenance
schedule. The epa estimates for that truck are 18 city/22 highway. and I do
about 60% highway.
Is this normal and the estimates are inflated?
100k on the a/f. That is not in the maintenance guide!!! If there was a
problem with fuel mixtture or fuel control sensors the CEL would be on, so
it is temperature, state of tune or driving habits/conditions.
You do not mention what tire size and type you have which can be a BOG
factor in MPG as well as the way you drive and the terrain you drive
in. BTW, if you read the actual EPA test cycle for highway MPG, they
never exceed 60 and the average speed for the 12 minute test is 48MPH.
Nobody averages 48 on highway except maybe in a city at rush hour (if
that) but it is how they weight the test to their favor for marketing.
If they used a higher more realistic standard, the "ratings" would be
lower. Newer test standards are in the works and while some claim
could MPG with those trucks, you have a lot of weight/mass there and
it take fuel to move it.
I think you've partially answered your own question right here. EPA mileage
is determined with stock sized tires with a narrow street tread in a
climate-neutral environment. Adding tires of a significantly different
size/width and a tread designed to grip soft terrain will lower your
mileage. In addition, I've seen air filters almost fully plugged with only
a minor change on the air flow indicator.
Here's some free advice. Do a lot of basic maintenance like air filter,
fuel filter, PCV valve, crankcase breather filter (if it has one). New
plugs and a basic tranny service with new fluid and a filter won't hurt
either albeit may not be absolutely necessary. Check your tires for proper
inflation pressure (low pressure can cause you to lose MPG). Run a street
tread in the warmer months and don't bother to measure mileage in any
conditions where your tires have to push their way through snow.
If your current tires are a different overall diameter than what came stock,
take your truck to the dealer and have them reflash the computer for the
current tire size because a speedometer error can be giving you false
readings when you calculate MPG.
And finally, I'm not saying that you have any of these habits but you should
drive conservatively - avoid jack-rabbit starts, hard stops and frequent
braking. Tailgating and other poor driving habits requires frequent use of
your brakes, which in turn requires more frequent use of your gas. And
finally, don't ride your brakes (keep your left foot on the brake and your
right foot on the gas).
Cheers - Jonathan
It could be normal. What you don't say is:
-has the mileage always been like this or is it slowly getting worse?
(need a tuneup)
-your average highway speed is 85 mph.
(probably normal fuel economy at that speed.)
-uphill in the mountains towing a boat
(you're getting good fuel economy.)
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.