30K maintenance - MPG dropped

[microjoe]

T4R gang,

I just had my 30K maintenance done about 2 months ago. The stealership quoted me $450 so I decided to do some of it myself. They did the differential fluid, transmission fluid and oil change while I did the spark plug and air filter change (they wanted $130 for the spark plug change alone). Everything went smooth and I replaced the plugs with NGK's I bought at the dealership. My V6 had half Denso and half NGK when I got them out.

Here is my problem. I have noticed the gas mileage has dropped pretty considerably since the change. I was getting about 18mpg around town before and am getting about 15-16 now. I doubt the fluid changes caused this but am wondering about the spark plug change I did. I did not think to check the gaps on the plugs as I was installing them, could a bad gap cause a mileage problem? I have not noticed a power difference, rough idle or anything like that, it is still as smooth as ever with plenty of power. If they weren't torqued properly could that cause a mileage problem? I snugged them and added about 1/2 turn (I don't have a torque wrench). Any thoughts out there?

 

[Jeff Kleb]

If they were not gapped properly, it could indeed affect your fuel mileage. Perhaps your spark is not quite "right" when they fire, and your computer compensates by allowing more fuel to be injected into the cylinder (and a richer fuel-air mixture results).

Just a guess, of course; but certainly a possibility. Sorry for your trouble, but it sounds as though a 79-cent gapper might have helped you.

The T4R.org Brain Trust will soon be along to help you.
:awais: :bigok:

 

[MW 4Runner]

I just replaced my plugs yesterday. I did notice under the hood there is an info sticker saying do not adjust the gap on iridium plugs. I checked mine on the new plugs (NGK) and they were about .40 - .42... I think the manual states the gap should be .44 I didnt bother to adjust them that little bit.

I too had a mix of 3 Denso and 3 NGK plugs. I checked the gap on my old ones and they were over .50 Don't know if that was from being worn out and needing replacement or if they were installed like that.

 

[Hank]

So what's the consensus on the gap? I'm gonna hit 60k soon and I've been wondering if the new plugs were pre-gapped. MW 4Runner, you said the ones you bought were between .40-.42, but you also said you got iridium plugs and not the regular ones for the 1GR-FE (I'm guessing you got the V6 since you got a mix of NGK & Denso). Just curious, how's the iridium plugs compared to the standard plugs? Notice any difference in fuel economy or power? Anyone else out there wanna chime in on this subject? I would like to know whether the new plugs should be gapped at .44 or just left alone. Thx n adv

 

[MW 4Runner]

In the manual it says for the 1GR-FE engine to use either DENSO (K20HR-U11) or NGK (LFR6C11). I bought the NGK one, it's not an iridium plug. I saw that warning sticker under the hood of my wifes car (it was after 11pm and I had changed her plugs right before I did mine :bonk: )

The manual says the gap is .043, so Im close enough.

 

[greasefingers]

No I do not think the plugs or the fluid is responsible for the drop in mileage. It is more likely a winter gas composition, low air pressure in the tires, or a very dirty MAF sensor.

Plugs come pre-gapped today. The never used to in the old days. I always check because of watching my father always adjusting them, when I was a kid. But I have never needed to adjust them in the last ten years or so.

 

[sharp4runr]

As well as winter gas, you also have ethanol being added to the gas mixture. And on top of it all, you're probably warming up the truck a little longer so that'll eat up gas.

 

[jharris2]

As well as winter gas, you also have ethanol being added to the gas mixture. And on top of it all, you're probably warming up the truck a little longer so that'll eat up gas.

Ethanol is not used everywhere, so it may be a contributing factor. But if it's used in the winter mix, wouldn't it also be in the summer mix?

 

[sharp4runr]

Ethanol is not used everywhere, so it may be a contributing factor. But if it's used in the winter mix, wouldn't it also be in the summer mix?

I'm envious of all you cats that don't have to use ethanol on your trucks. Ethanol sucks monkey butt. My bike's mileage has dropped about 10 mpg since they've introduced the crap in my area. I'm also seeing a drop of mileage in my truck.

Ethanol was introduced in my area this summer and I didn't notice the decrease instantly. I guess I just got used to what my truck was normally getting that I just didn't pay enough attention. Since I was riding my bike more in the summer I saw faster on that. It would drop almost 2mpg a month and now I'm hovering around 34mpg. When I got my bike early fall, it was around 40-44mpg.

 

[jharris2]

I'm envious of all you cats that don't have to use ethanol on your trucks. Ethanol sucks monkey butt. My bike's mileage has dropped about 10 mpg since they've introduced the crap in my area. I'm also seeing a drop of mileage in my truck.

Ethanol was introduced in my area this summer and I didn't notice the decrease instantly. I guess I just got used to what my truck was normally getting that I just didn't pay enough attention. Since I was riding my bike more in the summer I saw faster on that. It would drop almost 2mpg a month and now I'm hovering around 34mpg. When I got my bike early fall, it was around 40-44mpg.

Yeah, when I'm visiting family in the midwest, you can tell the difference in mileage. Figure we'll all be on it soon anyway.

 

[kimboy]

It may also be due to the change in temperatures. I know that starting my 4runner when its 30 degrees out is a lot different from when its 45.

I use the heater longer when its colder and blame that for the decrement in my fuel economy.