99 CRV, lower gas mileage after timing belt replacement

I am the original owner of a 99 CRV, 2 wheel drive. I have always
monitored the gas mileage closely - I mentally calculate it just about
every time I fill the tank - and it's always averaged about 25 mpg.
The mileage is about 112,000

About 6 weeks ago, I had the timing belt, water pump, and drive belts
replaced by a Honda dealership. They also changed the oil, replaced
the spark plugs, and the left engine mount, which they found was broken
when doing the timing belt work. Within the same week, I replaced the
tires (Costco, Michelin X Radial DTs) and had the front end aligned by
the dealership. I replaced the air cleaner myself.

Ever since this work was done I'm averaging 22 mpg. Nothing has
changed about my driving patterns. I've contacted the dealership and
they've told me that it is not possible that the work they did caused
the gas mileage reduction. (I consider this to be a reputable shop,
I've had work done there several times over many years) The advisor
also implied that this really wasn't anything to be concerned about,
and there really isn't anything that they can "check" to find the
cause. As I told him, I disagree, this is >10% reduction in gas
mileage which is going to cost me about $250 / year.

So I'm hoping an expert can advise, is it really just a coincidence
that my gas mileage dropped after this work?

 

Could be just a coincidence.

Did they put in plugs that Honda recommends?

How old are the ignition wires?

Have you checked the inflation pressure of the tires?

Other tips:
http://home.earthlink.net/~honda.lioness/id11.html

 

Perhaps the ignition timing changed and needs to be retimed.

 

If the cam wasn't aligned right, the valve timing is off. That will
affect mileage as well as performance. The adviser just wants you to
go away, it sounds like. It is also possible that your new tires have
much higher rolling resistance compared to your old ones, but I doubt
you'd see such a marked change from tires alone.

 

There are way too many variables here. Is your engine idle speed about the
same? Is it possible the dealer un-aligned your vehicle's tow in? Has the
weather gotten colder? Different tires, new timing belt, tune up.... Why
not find out what other compariable Honda's are getting mpg wise. Lastly,
is it possible someone put the wrong type of oil in your engine?

 

it's possible cam timing was messed up, but i'd expect more than 10%
drop in gas mileage if it were out a tooth. other things like brakes,
tires, ignition componentry can /all/ affect mileage too. have all
those checked, and if after that, you still think it's timing belt, use
a timing light to check ignition timing yourself. study the steadiness
of the timing marks under the strobe. [need to do this with the service
jumper connected.] if the timing is wavering back and forth while
idling, the belt is loose. it appears to be a fairly common rookie
mistake that will affect mileage pretty much like you're experiencing.
take it back and make sure a more experienced person re-tensions it.

 

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jmattis sounds the closest.

Does it start and idle EXACTLY the same as before, or does it hesitate a
bit until it warms up? I would have guessed you have one or the other of
your cams out of time, or you started buying your gas at a place that
sells 'winter blend' gasoline.

You know you should be getting the valves adjusted every 30,000 miles,
right?

'Curly'

 

Maybe it wasn't the work done on the engine that is causing the drop
in fuel economy. Any chance the work done coincided with the warm
weather/new fuel (alcohol) blend?

The gas mileage on both of my cars( '91 Accord and '01 Acura CL-S)
would drop exactly 10% when the MTBE was added around April and
recovered in October/November when the winter blend was available.
My guess is that the alcohol blend will be similar. I've noticed a
slight drop in fuel economy recently but my driving habits have
changed and would not be a before after good comparison regarding
fuel.