I realize it's summer, but I really can't find a good reason for my fuel economy to drop as much as it has since May. Last year, my average of roughly 32.5 MPG took a 3 MPG hit during the hottest months of summer (July-September). This year however, my Fall/Winter/Spring average has dropped to about 26-27 MPG since May. I can't find anything wrong with the car - tires are new and inflated (maybe a little over-inflated), air filter and plugs are good, oil is changed regularly, AC works like new, no CEL, my commute is the same as it's always been, etc.

Are the gas suppliers thinning out the fuel with ethanol, maybe?

Just wondering if anyone else has noticed as precipitous a drop.

2007 Base Fit with 5MT.

 

if the gas companies are thinning out our fuel with more ethanol i am going to freak.

 

Because this year's Texas temperatures are 3.5 degrees above average. Presumably you use AC in your car, and you're using it slightly more than normal to maintain the same semi-comfy interior temperature.

Ethanol max % is on the side of the pump. The company can mix up to that amount, but doesn't need to - in places like Texas you are so close to the refined gasoline that it's traditionally been lower in ethanol than in, say, the "corn states." Whether that has changed recently, I don't know.

Just as an aside, we now put half the US corn crop into our gas tanks. It's so sad that we grow such massive quantities of a crop that is a) a huge use of scarce water and soil nutrients and b) uneconomic without government subsidies - meaning, of course, that you and I and everyone else paying taxes is paying people to grow corn that otherwise they would not choose to plant. And all so we can get worse fuel economy and, if they take the % up enough, dissolving engine seals. I don't really see the sense in this, but, I guess that's why I don't walk the corridors of power. :P

 

If you think it's an ethanol problem well try a higher grade of fuel. Usually 91 gas is ethanol free. Check the supplier to make sure (Heck ask the gas station attendent). Then compare your MPG's.

No doubt we are experiencing a hotter than normal summer as well. Hot air and engines do not produce the best conditions for good fuel economy. Does it explain such a big drop. Not in my opinion.

There are some preventative things you can do like a good K&N filter to improve air flow. Check your plugs, clean your engine bay, get better oil, make sure your tires and suspension are in good shape. All the regular things. Sticky brakes?

Maybe it's a combination of several factors?

Sometimes a good old fashion tune-up?

But hey maybe you're a car nut and you keep your Fit so clean and tidy and in perfect working condition that maybe it really is just the ethanol!!!

I would be curious to know your next steps.

Dwayne

 

Well, like I said in the original post, compared to last summer, which was actually quite a bit hotter than this summer, it only dropped about 3 MPG during the hottest 3 months.

On my way home today I'll get some Techron and have them run an OBD scan. I'm curious about the O2 sensors, really. I suppose it might also need a valve adjustment. It has about 87k miles and has never had it done. Before popping the valve cover though I might try running some higher grade gas for the next tank, just to see if that affects anything. Maybe overinflate the tires too, say up to 40 PSI (at 38 now)? Maybe some DIY ducting to get more ambient air into the intake?

Could it be the coil packs? The car feels a little down on power, but with the AC on and only 109 hp, that's HIGHLY subjective!

 

Hope this makes sense:

If you mod your car for better air, over inflate your tires etc then you are just covering for another deficiency in another component or system?

I think you have a good list of things in your post to check first.

There are so many consumables on cars to wear out and can then affect gas mileage...I think it's almost impossible to logically figure out what the main culprit would be.

I suspect worsening gas mileage over time has to do with the degradation of parts, driving conditions, and user preferences ( i.e A/C use).

 

Are the gas suppliers thinning out the fuel with ethanol, maybe?

Just wondering if anyone else has noticed as precipitous a drop.

2007 Base Fit with 5MT.[/quote]Hi all newbee here. I traded a 2010 sport for a 2012 base fit. My 2010 model was just before the nitro fil. I was getting 38mpg before the nitro and went to 40 after the nitro. I drive with an eye on the fuel economy gauge. My 2012 has never gotten over 38 and has been running 32 to 34. I live in central Florida and have under 7,000 mikes on the car. Maintenance was done right at 5,000 and I have not seen any change.

I did notice a slight improvement in 1 tank of gas that I bought in Miami, but it was all highway miles. In past years it seamed like when gas prices went up the fuel economy went up as well. So say it is just a subconscious light foot in reaction to the increased cost. I think the gas company's add a little extra octane when the prices go up.

 

You definitely need to do your valve adjustment. I did mine at 70k and replaced the air and cabin filters while I was at it and I went from 31-33mpg up to 35-37mpg.

 

I don't hear any valve clatter... is the only way to tell to pull the cover and whip out the feeler gauges?
Blecch.

 

I just got my (2007 Base) Fit a month ago so I'm not quite sure what's normal yet. I've been getting only around 26-30mpg though, and seeing as I drive it pretty conservatively, that's less than I'd expect. Yesterday my check engine light came on and I took it somewhere to get the code read. Two of the things the guy mentioned were the O2 sensors and the coil packs. I don't know much about those yet, but if one of them is faulty and fixing it would improve my MPG, I'd be thrilled! Keep us updated if you figure out the problem.

 

I'd suggest getting a valve adjustment. Even doing it yourself if you have the right tools. It took me 30 minutes to do my own.
Tool list:
10mm socket ratchet
10mm wrench
Standard screwdriver
Feeler gauge
RTV sealant
Torque wrench

Texas weather varies. In Dallas this year, it has been much cooler than it has previous years. Certain days will spike, but most days are bearable.

I run 93 octane from Shell stations or Exxon stations. I have seen a drop in my mileage even though I'm boosted. Usually I'd get 240 a tank(9gallons) and now averaging 220 a tank or less.

I was going to remove the cabin filter, it's probably filthy, but removing it would help my a/c in the hot summer.

 

Bluecell.

Did your valve adjustment fix you MPG problem?

And at what mileage do you recommend Fit owners check their valves?

Many thanks.

Dwayne

 

I'd have to say there was some improvement, but nothing crazy. If anything, you'll get any loss of power you lost back. I do think the cabin filter does a lot for you since a/c is a main issue during the days.

 

So to improve or maintain your expected MPG you recommend changing the cabin filter once a year....makes sense.

 

^ oh wait you're canadian lol, but still. A dirty filter is a dirty filter and what happens when its clogged? No air flow.

To answer the other question, somewhere between 50k-75k miles to check valves. I've checked mine twice. First time to loosen it as much as possible, but within spec and 40k later I hear some chatter, so I made it as tight as I could this time. Loose is more power.

 

Tires are new? same size? weight different? (check Tirte Rack or tire manufacturer of tires to see). Over inflation by 5 lb will generally increase mpg. Heavier tires or bigger size will reduce mpg. Lots more a/c will kill mpg. I doubt TX allows ethanol but if so the pump should be so labelled. Then of course there is the tendency of refiners to reformulate gas recipe to get more gallons per day output that reduces the combustion energy per lb.

 

Well, I managed 29 MPG, but almost half of those miles were on the highway, so it's still not great. I went ahead and overinflated the tires a couple more psi, and filled up with 93 octane, just to see if there's any difference.

Initially, and maybe this is just warped perception, the engine seems to be a little more "on". Less stumble when I don't feather the clutch from a full stop, and there seems to be a little more immediacy in throttle inputs.

Cabin and intake filters are both new as of this spring. I swap those out every April.

 

Anyone here getting more KM out of the first half of the tank than the last. I don't run that low to find out but see it drop 1/4 tank faster below half then on the way from FULL and I dont TOP up, but do let the tank settle 18 secs before I finish filling up.

 

The gage is not linear, that is the gage does not read half full when half the gasoline is left in the tank. In most vehicles about 60% of the gass is consumed when the gas gage shows half.
as others have said, be careful of filling the pipe from the gas cap to the gas tank; filling too much does let liquid gas into the absorber canister.

 

Why? what does the cabin filter have to do with engine performance?