Fuel Economy Tuning 101

[TypeRNammer]

Currently my del sol is only doing about 9l/100km in the city which is higher than normal, on the d16z6 motor. (About 425km's a tank)

My mods on it are just the basic bolt ons, intake, header, exhaust.

Not sure why my car is getting crappy mileage. I've already done the basic tune up which consists of the following...there might be more but can't remember them all

-synthetic oil changes
-spark plug wires
-spark plug
-fuel filter
-pcv valve

I checked the brakes on all 4 corners and all my tires spin freely.

Tire pressure is 33psi all around.

My driving habits are normal, so no sudden acceleration or braking, keeping a consistent speed.


If anyone can chime in that would be great, thanks!

Feed back would be greatly appreciated if I missed out on any other maintenance for better fuel economy.

[fliptuner]

-clean your intake manifold (fogger)
-check the condition of your cap and rotor
-air filter
-check your o2
-clean your injectors with a 3m kit

[TypeRNammer]

thanks i'll keep that in mind i have changed the air filter and cleaned my fuel injectors. I think i would need to replace my o2 sensor soon too.
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[shenmecar]

Clean the throttle body?

[TypeRNammer]

Originally Posted by shenmecar

Clean the throttle body?

I will check up on that soon

[SumAznGuy]

What oil are you using?
On my S, I was getting 11L/100km with Rotella T 5W40 oil.
When I made the switch to Motul 8100 10W30, my mileage improved to just under 10L/100km's. On a good week, I can hit 9.8L/100km's.

Also, what tires are you running? A wider/stickier tire will reduce your economy.

Check and see if you have a leaky injector, or a stuck injector. My old CRX si use to get 550 km's per tank then dropped to 425ish per tank when I had a leaky injector.

Also, try changing your transmission fluid, if you haven't done so. Newer fluid should allow the tranny to run smoother which will help a little bit.

[TypeRNammer]

Originally Posted by SumAznGuy

What oil are you using?
On my S, I was getting 11L/100km with Rotella T 5W40 oil.
When I made the switch to Motul 8100 10W30, my mileage improved to just under 10L/100km's. On a good week, I can hit 9.8L/100km's.

Also, what tires are you running? A wider/stickier tire will reduce your economy.

Check and see if you have a leaky injector, or a stuck injector. My old CRX si use to get 550 km's per tank then dropped to 425ish per tank when I had a leaky injector.

Also, try changing your transmission fluid, if you haven't done so. Newer fluid should allow the tranny to run smoother which will help a little bit.

Current oil I am using is Mobil 1 Synthetic paired up with a Wix Oil filter.

Rims/Tires Combo is the XXR 501's 15x8 et15 with 205/50/15 Kumho Ecsta ASX (This setup definitely might factor in for the gas mileage)

As for leaky injector, how would I be able to check that?

I recently change the transmission fluid not too along ago, switched from Honda MTF to Redline MTF.

[SumAznGuy]

When was the last time your car went through air care? A leaking injector would most likely have messed up the emmissions and your car would fail.

Definately going up to a wider and heavier wheel combo will affect your fuel economy. I believe stock, your tire size was 185/60/14 which would be less contract friction and weight of the wheels.

Has your car always been around 425 km's per tank or did it change recently?

[TypeRNammer]

Originally Posted by SumAznGuy

When was the last time your car went through air care? A leaking injector would most likely have messed up the emmissions and your car would fail.

Definately going up to a wider and heavier wheel combo will affect your fuel economy. I believe stock, your tire size was 185/60/14 which would be less contract friction and weight of the wheels.

Has your car always been around 425 km's per tank or did it change recently?

It went through air care 1.5 years ago.

When I leave the car idling for a while, my exhaust really stinks, most likely I'll need a new cat after I barely pass my last air care test.....or maybe that leaky injector you're talking about!

I should start looking at a lighter set of wheels now after winter that is!

Before it was would be anywhere from 475km - 525km per tank, but now it's 425km's or less.


Thanks for the input, all of this info should be able to help me and other RS members on the board

[fliptuner]

If you plan on driving it through the winter, I'd suggest picking up some cheap, stock sized rims. 14" are cheap and you're definately going to gain some economy from the weight loss and less friction. That and you won't be wearing out you're summer wheels.

[sonick]

Does the exhaust smell like sulfur, or smell like raw fuel?

If former, could be the cat.

If latter, could be the O2 sensor causing it to run rich and not fully burning fuel.

[TypeRNammer]

Originally Posted by sonick

Does the exhaust smell like sulfur, or smell like raw fuel?

If former, could be the cat.

If latter, could be the O2 sensor causing it to run rich and not fully burning fuel.

I think it's more of a raw fuel smell, either way it smells like shit

[ncrx]

could be either 02 sensor or thermostat, if ur stuck in cold idle mode u'll drink fuel, or if ur 02 sensor is weak or dead u'll get shitty fuel economy, or lastly ur cat is clogged and your engine is working harder to keep the same pace

and also cold temps meaning warming up takes twice as long , fuel economy is reduced

[godwin]

For cars that has distributor.. clean that. Also check for vacuum leaks..

[TypeRNammer]

Originally Posted by ncrx

could be either 02 sensor or thermostat, if ur stuck in cold idle mode u'll drink fuel, or if ur 02 sensor is weak or dead u'll get shitty fuel economy, or lastly ur cat is clogged and your engine is working harder to keep the same pace

and also cold temps meaning warming up takes twice as long , fuel economy is reduced

my thermostat is in working condition

o2 sensor i'll definitely look into that.

the cat i will have to replace very soon since my aircare is coming up.

Originally Posted by godwin

For cars that has distributor.. clean that. Also check for vacuum leaks..

So far no Vacuum leaks

And I will take a look at the dizzy also

[godwin]

What you are saying is you are using a thicker oil and you are getting better mileage?

Originally Posted by SumAznGuy

What oil are you using?
On my S, I was getting 11L/100km with Rotella T 5W40 oil.
When I made the switch to Motul 8100 10W30, my mileage improved to just under 10L/100km's. On a good week, I can hit 9.8L/100km's.

Also, what tires are you running? A wider/stickier tire will reduce your economy.

Check and see if you have a leaky injector, or a stuck injector. My old CRX si use to get 550 km's per tank then dropped to 425ish per tank when I had a leaky injector.

Also, try changing your transmission fluid, if you haven't done so. Newer fluid should allow the tranny to run smoother which will help a little bit.

[godwin]

oh don't forget simple timing etc

[SumAznGuy]

Originally Posted by godwin

What you are saying is you are using a thicker oil and you are getting better mileage?

I went from the Rotella T oil to a Motul oil and got better fuel economy. You can call BS all you want, but I've gotten the same numbers numerous times and am pretty confident that these numbers are reproducable on my car.

I asked a friend of mine who is a Motul rep and he said this was something that other people have said as well.

[ncrx]

Originally Posted by godwin

What you are saying is you are using a thicker oil and you are getting better mileage?

Do you have any idea on how to compare oils? I bet you assumed the 10w30 was thicker than the 5w40 b/c of the cold weight. The rotella is a far thicker oil, the Cst rating at both the 40c and 100c measurement. the Motul is significantly thinner oil. The rotella which i use is on the heavy end of the 40 weight oil spectrum approaching a 50w.

A 30-weight oil is between 9.3 and 12.4 cst at 100C. A 40-weight oil is between 12.4 and 16.8 cst at 100C. The weight classification shouldn't be used to compare oils, only at a general level

[godwin]

Let me clarify my statement the OP stated that he gained ~10% mileage improvement just by changing the oil alone. That's a huge difference for such a small incremental change. Granted internal friction plays a role in mileage reading, but not it shouldn't be that noticeable.

What I am suggesting there are other extraneous factors at work here.

Originally Posted by ncrx

Do you have any idea on how to compare oils? I bet you assumed the 10w30 was thicker than the 5w40 b/c of the cold weight. The rotella is a far thicker oil, the Cst rating at both the 40c and 100c measurement. the Motul is significantly thinner oil. The rotella which i use is on the heavy end of the 40 weight oil spectrum approaching a 50w.

A 30-weight oil is between 9.3 and 12.4 cst at 100C. A 40-weight oil is between 12.4 and 16.8 cst at 100C. The weight classification shouldn't be used to compare oils, only at a general level

[SumAznGuy]

Originally Posted by godwin

Let me clarify my statement the OP stated that he gained ~10% mileage improvement just by changing the oil alone. That's a huge difference for such a small incremental change. Granted internal friction plays a role in mileage reading, but not it shouldn't be that noticeable.

What I am suggesting there are other extraneous factors at work here.

I thought so too, but alas, these numbers were repeated many times. My last oil change 5000 km's ago, was with Rotella SB. Gotta check the weight of the oil, but I was getting around 360-380 km's before filling up with 40L of gas when the oil was fresh.

Also, look at some of the newer cars. To get the internal friction down, and increase mpg ratings, car companies are using 5W20 oil. There is a reason for that.

I am going to go do an oil change tomorrow, and was thinking of going back to Motul 8100. I was thinking of going to a 5W30 this time as it is getting pretty cold.

All my numbers have been with the car pretty much the same. Same plugs, same everything other than the oil. Most of my driving is done in the city with normal stop of go traffic. I live in Burnaby and work downtown so it is pretty much the same drive everyday.

I tried keeping track of the numbers last year, and even seperated the numbers while running on my 17's and on the stock 16's with snow tires.

[ncrx]

i can believe a 10% loss in economy from switching to rotella. If you're driving in the city only on short trips with a lot of stop n go, 10% is believable. Many rotella users take a hit in the mileage anywhere from 2-3mpg. Unless you get the motor and oil really hot, rotella is pretty thick.

[SumAznGuy]

Originally Posted by ncrx

i can believe a 10% loss in economy from switching to rotella. If you're driving in the city only on short trips with a lot of stop n go, 10% is believable. Many rotella users take a hit in the mileage anywhere from 2-3mpg. Unless you get the motor and oil really hot, rotella is pretty thick.

I wouldn't say I got a 10% loss from switching to the Rotella. I was use to getting around 11L/100km's with dino oil, Mobil 1, and Valvoline. It was when I switched to the Motul that I got the car to do 420/430 km's on a tank.

I didn't mention it, but I got the same results when using the 300V and 8100, but I don't think too many people here are going to run out and buy 300V for their cars. I only used it because I was preping the car for a hot date out at Mission.

Maybe I should start logging my mileage again.

[ncrx]

the 300v won't hold up to daily driving like the 8100, but the 300v would be good for a track day. the 8100 has more additives to last for longer drain intervals.. whereas the 300v doesn't contain very much.

i'd say you'd have to compare the cst values across all those oils at 40 and 100c to see perhaps the motul oils are a bit thinner than the others.

[TypeRNammer]

Any recommendations for fuel filters? The last thing I want is garbage no name shit from lordco lol
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