well my other thread was closed because it wasn't a "technical" question when in reality it was i was just unable to respond to my own thread quick enough! LOL


So i have 2 d16y7 cars and i was asking what avg. gas mileage these things get because i have one that is runnin 36mpg while the other only gets about 23-25mpg.

The hatch thats getting the bad mileage has no CEL and has no idling,running,or any issues that are noticeable.

Just trying to figure out why one gets almost 40mpg and the other just shy of 25 mpg, what could i be missing in this situation.


anyone have any idead?? lets discuss d16y7 mpg help! lol

 

Wear and tear. Maintenance, or lack thereof.
Try a side-by-side compression test.

 

whats strange is i bought the 2 hatchbacks from the original owner and the service dates and the services rendered on each car was almost identical. All work was done at the local dealer!

ond car has 302k and the other has 307k miles!

 

No clue then. Did two separate people drive these?

 

What kind of mileage is on both engines? What transmission are mated to each? What chassis are they both in? That discrepancy almost makes complete sense, if one is an autotragic in an EX sedan, while the other is a standard in a CX hatch.

Everything else the same though, grumble is on point. Wear and tear, basic maintenance, age.

edit: guess I type too slow. Do the side by side leakdown comparison like grumble said. Not all engines wear evenly, even if driven by the same person.

 

^^ 302K on one car and 307k on the other

Both are dead stock original hatchbacks one is a 96 DX 5 speed the other is a 97 DX 5 spd. both d16y7's unfortunately

 

2 different people drove them

 

That's your variable other than the one year difference.

 

Check the air filters also.

 

30+ is about right. I get 30-35 on my DX Sedan (D16Y7) with no WOT just lots of cruising and hypermiling. Then again, I've changed the spark plugs, wires, distributor rotor/cap, o2 sensors, changed the headgasket, timing belt, water pump, etc; in the past 12 months. Mileage is much better as to when I first bought it.

 

If you have been keeping up with your regular maintenance schedule....Get a Scan tool dude....

If you dont already have one and have a smartphone...get the $20 Bluetooth OBD2 adapter and $5 Torque App....Those 2 together are basically a scan tool.

Check all of your sensors that go to your ECU. When I first bought my 98 CX a few months ago, I was averaging 30ish MPG. I mean 30 MPG is still good right??!? Thats what I thought coming from a Camry.

Then one day my ECT sensor threw a code......I cleared it and it went away....a few weeks later when I was taking readings from my scan tool, I noticed my ECT sensor would jump to 0 for a few seconds here and there. Afterwards, it would go back to registering normal temp. I could hear the engine idle high whenever the ECT sensor would jump to 0. I went ahead and changed it and noticed a nice jump in MPG to 32.

A few weeks after that....I noticed my O2 sensor voltage was rocking back and forth out of tolerance (from 0 to 1.3V, when it should be from .2 to .8ish). I wasnt getting any codes. Upon inspection of the sensor and wiring I discovered that the previous owner had spliced in a junkyard O2 sensor (probably from a completely diff vehicle since it was spliced). Whenever I pushed my thumb on the splice, it would jump like crazy. Since the O2 sensor already comes with the wiring. I just replaced the whole O2 sensor and now im rocking 36 MPG!!

I never realized how much influence each sensor and the ECU have over MPG. So before you go ahead and throw a bunch of parts at it, drive around a few weeks with a scan tool attached to your car. It'll tell you a lot!

 

i have a snap on solus

 

different drivers?

I find it hard to believe low to mid 20s is even possible with a d series. my 4 door 97 ls gets consistently over 30mpg.

 

Aren't they both getting swapped anyways?....

 

Maybe he's reconsidering. Or just curious.

 

Tune up stuff like plugs and wires ect, fuel filter, condition of the injectors, condition of the intake (clean or dirty), condition of the valves and bottom end, how they are driven (do you drive one like a race car and the other like a granny), condition of the coil, condition of the O2 sensors all these play a role in fuel economy.

 

yes one is getting a b20b4 swap and the other is getting a h2b. but for the time being the cars are both being used so i am basically testing them to be sure that whoever i am selling these d16y7 swaps to is getting what they pay for.

the one that is getting f'ed up mileage has a bad ISB but that wouldn't effect any mpg by no means.

 

Tires!!! I keep screaming this to everyone, you can have up to 3% better gas mileage with a better tire vs an old worn out tire. Also, the very obvious things that grumble has pointed out; different drivers, one years time, compression can also be a variable for internals which may not cause a CEL, also fuel filters and timing being off could be a factor even a degree or two.

 

^^^ Where'd you get 3% from?

 

3% is actually a low ball number, 3% better fuel economy on something that gets a rated 35 ish mpg would only be a difference of 1.05 increase which is low considering having a good set of tires vs some worn out crappy unbalanced ones can lose upwards of 2-5 mpg depending on several other factors (driving habits, weather conditions, etc.). So, 3% isnt much at all.

 

I think he's asking how you connect tires to a percentage of MPG. If he's not, then I am.

 

?? my tires are fine.

 

Question is.. how couldn't you connect it to a percentage? I mean given the fuel filter is slightly clogged could account for let's say 2.5% fuel economy based on what the vehicle is rated at. It's quite simple actually. You could do it with a number of things but being as several other factors contribute to the tires being a fault with gas mileage it's far easier to put it in a percentage vs just an outright figure. But if need to be simply put, if your tires were dang near bald and were horribly out of alignment could cause you to lose anywhere from 2-4 mpg (or roughly 6-10% of your estimated mpg). Better? I've just done engineering design for LRR (low resistance tires) tires and we use a lot more percentage graphs and such to calculate than raw figures. So, sorry if I was a little vague. He says tires are fine so go with all other things mentioned by Grumble.

 

I mean, how can you say that new tires will net you "whatever" percent? How are you even calculating that? Where are you getting these numbers from? Is there some formula you're using?

 

The driver is the biggest MPG variable. Driving conditions is another. If you have 2 different people driving the cars for 2 different style commutes, that is your difference. Try swapping cars for a couple weeks and see if the MPG numbers follow the driver or the car.

If we assume same driver and same commute, the variables are the health of the engine (compression), fuel, tire tread, tire pressure, tune-up, weight, etc.