MPG heading south


#1

04 Toyota Matrix got 32-35 mpg at speed-new

4 yrs later and 85,000 we got 27mpg on a

500 mile round trip- today.

Thought about ‘tune-up’ but it isnt on the

“schedule” until 120,000 miles. (probably,

do plugs anyway) any suggestions ??


#2

these extended maintenance intervals as recommended by the car makers are pure garbage imho.
it’s done for no other reason than to give their cars the appearance of needing less maintenance.

the plugs (more than likely the reason for the mileage drop) should have been changed about 35k miles back - along with the fuel filter, air filter, transmission fluid, etc.
jmho anyway.


#3

Has anything been done to the engine? New spark plugs? Anything?

Ethanol in the gasoline is probably responsible for some of the mileage loss. My experience is that e10 (10% ethanol) results in a 3-4 mpg decrease, but that does not account for your loss.

I suspect it’s time for some vehicle maintenance. Air filter? Spark plugs? Oil change?

Does this vehicle have an automatic transmission, or a manual?


#4

You need to check:

  1. Plugs- even though they may not be recommended yet, as plugs wear, the gap widens and the spark weakens beacuse it has to jump a widen gap. You may also have fouling.
  2. Plug wires- an old plug wire can also give weaker spark.
  3. Filters- air, fuel, etc. Especially a clogged air filter can kill mileage.
  4. Tire pressure- low pressure on any tire can drive mileage into the ground.
  5. PCv valve- a clogged valve can cause issues.
  6. Valve clearence- if your valve clearence is off, it will cause poor performance.
  7. Ignition timing- if this vehicle has a distributer, you need to check the timing. The on board computer can compensate if it’s off but at the expense of mileage.
  8. Have you changed where you get gas recently? If so, you may want to try a different station…could be poor quality gas.
  9. Lastly, check your struts. A worn strut can affect mileage as can alignment issues and tire issues.

You have put alot of mileage on this vehicle in 4 years. Doing maintanence before the recommended intervals may be a good idea. If you have a regular mechanic, consult them or talk to your dealers service dept. They may recommend different intervals for service.
Good luck!


#5

we did change all the trans/ transfer and diff fluids to synthetic blends this winter. Including the engine oil.
Air filter was changed but I cant recall the fuel filter - that will be on the list.
Does anyone consider plug wires and caps any more ??
tc


#6

ok
plugs for sure
fuel filter, (we check the air filter regularly with oil changes),
tires are right on – just took off the snows yesterday
We do have winter fuel up here. It was 14F when we left this morning and warmed up on the way back.
pvc shall be changed as well
As i said above–we changed all trans and diff fluids to synthetic blends
Last year we had to change both rear wheel bearing assemblys ($300 ea)
tc


#7

I think the combination of cold weather and “winter fuel” accounts for 90% of your gas mileage reductions.


#8

Don’t bother “checking” an air filter. They can look good and still be highly clogged. They can look bad and still be good. On some cars they are designed to seal in such a way that checking them can cause the seal to fail. Just replace them at the specified interval or sooner. (especially sooner if you live in a dusty area)


#9

I’m not sure the '04 still had plug wires. I believe Toyota was using “coil-on-plug” also called “distributorless ignition” by then. Rather than have one coil the output of which is sent to the plugs through plug wires, coil on plug systems have an individual coil on each plug, each coil fired by the computer at the appropriate time.

If I’m right only the plugs and filters (fuel and air) need be changed.


#10

First that is only a 16% decrease and it was only one trip. Did you have a headwind both ways?