Gas Mileage Issue in 2002 LE

[Indigo]

Hi all! Wondering if I could get some input on an issue I've been having.

A year and a half ago, I bought a 2002 LE Corolla with 92,000 mi on it. When I got it, it was in good condition, and just needed a few repairs (like a new serpentine belt). Over the past 18 months, I've put on about 9,000 mi on it and done a few repairs with a car-savvy friend. We've put on new brake pads and rotor on one of the front tires, replaced the caliper on that same tire, changed the oil a couple times, flushed the brake fluid and the coolant as well. All in all, it's a fantastic car, and I've really enjoyed learning about the process of taking care of it.

Funnily enough, over the past few months (starting in around October, November), I noticed a significant drop in gas mileage. Normally, on the highway it would get about 35 mpg, and around town it would get close to 30. But ever since late fall, I've noticed a significant drop. The highway range varies anywhere from 30-35 mpg, but around town, I'm lucky if I get 25 (typically, it's in the low 20s). I was wanting to write it off as a fluke, but it's persisted over the past few months, and I'm not really sure what to make of it. I've kept my eyes and ears peeled for any abnormal sounds, sights, or smells, but nothing has indicated that anything is wrong with the car, aside from the drop in mileage.

Does anybody have any idea what might be going on? My friend's no longer in town, so I can't use him as a resource, but I'm more than willing to take it into a shop to get it looked at. Another friend wondered if it might be one of the drum brakes for the back wheels, but I haven't noticed the car pulling to one side or the other. Unfortunately, I don't have service records from the previous owner, but I'd be happy to supply any information I have that might be helpful.

Thanks in advance!

[mickburkesnr]

First thing: you shouldn't just replace the rotor on one wheel. It should always be done in pairs. Same with the brake pads. If you do the left, you do the right.

As for the mileage, how are you calculating the MPG? Are you going by what the car's computer is telling you?

Here are a few things to consider:

• Have you changed fuel supplier? I notice in England a tank full of Asda supermarket petrol doesn't last as long as petrol from other places.
• Are your tyre pressures correct?
• Has your driving style changed?
• What condition are the tyres in? Do they have enough tred?

I would work out your MPG properly, ignoring the computer if thats what you're using. They're notoriuous for being wrong.

[Indigo]

Good to know with regards to brake pads and rotors;  I'll keep that in mind.

I calculate MPG by hand.  My car is too old to have a computer calculate it in the first place, but I always update the trip meter and punch the numbers in by hand every time I fill up the tank.

Fuel is an interesting one.  I guess I haven't really thought about it, but I've mainly been getting my fuel from a particular type of station.  Let me try and change it up and see if that makes a difference.

Tire pressure I check consistently.  Ever since I got stuck with a flat in the middle of nowhere, I make sure I have a portable tire inflator.  I also have a separate gauge (so I'm not just relying on one type of measurement).

Driving style (as far as I know) has not changed.  I'm generally a pretty defensive driver, and whenever I'm on the highway I cruise at around 2500 RPM.  Certainly nothing drastic.

Tires are in decent condition, nothing to write home about, but not bald by any means.  Could probably stand to get some new ones in the not too distant future.  But if the issue were tire wear, it would be strange to me that the drop off would happen suddenly (which is what happened) instead of a gradual decrease.

I don't know if this information makes you think any differently about things, or have any follow up questions.  If so, please fire away.  As for right now, I'll make sure I fuel up at a different station and see what results I get.

[Heidfirst]

How cold does it get where you are? Over winter it takes longer to get up to working temperature & you tend to use lights/heating/aircon etc. more which all contributes to losing a few mpg (& I am guessing that you are in the US where you have a smaller gallon to start with?).

[Indigo]

Yeah, I live in Maryland, USA.  I'm originally from Vermont, so I'm used to the colder weather and the effect it has on my car.  The weather this year has been rather erratic (especially for the past couple months), but what's strange to me is that I didn't notice this problem last winter, when the weather was roughly the same.  It might be that I'm a little more impatient this year (and not letting my car warm up enough before driving it), so I'm keeping track of whether this situation improves as the weather gets warmer.

[mickburkesnr]

The thing with tyres I've found is that you can be driving on a wet day on a Monday, go round a corner and be fine. On Tuesday in the same wet weather on the same corner you can feel the car slide. The tyres when they wear down start to lose grip. Cheap Chinese no name tyres are also horrible. But where the rubber meets the road can affect MPG. To what degree I don't know. But like I said grip can go down.

Heidfirst makes a good point about the weather. Regardless of letting the car heat up you'll be using the heater more and the headlights. These require power, and that comes from the engine. So the more electrical gadgets in your car, the more your mileage could suffer.

Plus, how often did you check the MPG? After every fill up every week? It might be a case it hasn't dropped off a cliff it might be that you've just noticed it? But I think fuel brands could be a factor. Depending on where you go if the petrol station isn't a major brand but instead buys its petrol as wholesale you could be filling up with a different mix of fuel compared to what you had before, even though it's from the same place. I think supermarkets do this in the UK, or smaller independent stations do. Places like BP/Shell will obvious have the one mix.

[Indigo]

No, those are good points.  I do make a point to check the MPG every fill-up.  It's something my brother taught me to do, so it's developed into a habit.  Generally, I fill up the take every 7-14 days (I live in a small city, so I don't need it every day, but I do use it pretty regularly).  

Let me go and check on the tires again just to confirm on their status.  It could be that I just haven't noticed significant wear.  The car is still handling all right, but it's worth another evaluation.

I do appreciate the input and questions, for whatever it's worth.

[oldcodger]

6 hours ago, mickburkesnr said:

I notice in England a tank full of Asda supermarket petrol doesn't last as long as petrol from other places.

 

Bit surprised at that,  used standard Shell for 2 years and Asda for years since , no difference in mileage, still the same 38 - 42 mpg,  winter /summer

 

Quote

I would work out your MPG properly, ignoring the computer if thats what you're using. They're notoriuous for being wrong.

Agreed, filling the tank right up is the only way.

[oldcodger]

23 hours ago, Indigo said:

. Another friend wondered if it might be one of the drum brakes for the back wheels, but I haven't noticed the car pulling to one side or the other.

The simples way to check if the brakes are binding, is after a long run,  get out and carefully place yor hand on the centre of the outside of the wheel / hub cap and see how warm /hot they are;  do not try and touch the disc /drum itself !

The fronts should be quiet warm to hot, but equally on both sides, the rears should be cooler.

Any wheel that was dragging, you would expect it to feel much hotter.

As you do not seem into doing a lot yourself, best to get a garage to lift up the car and spin each wheel to see if any one is dragging; or even put it on a rolling road machine to check how effective all the brakes are, should be a quick and low cost job.

[mickburkesnr]

12 hours ago, oldcodger said:

Bit surprised at that,  used standard Shell for 2 years and Asda for years since , no difference in mileage, still the same 38 - 42 mpg,  winter /summer

So was I because I never bought in to the whole different brand thing, but when I put Shell or Sainsbury's petrol in I get about 320 miles out of a tank. When I put Asda's stuff in I only get 300. And my commute is fairly standard, like there's no one day where I'm either standing still or driving faster than any other day.