Just a question?

[Jason8691]

I have read alot of posts on this site and sometimes end up pretty confused about which oil to use! Anyway, I had been running Amsoil 0W-30 in my 4.3L Chevy engine and got a steady 15 mpg's on that oil. Due to a dealer mixup (they drained my oil and changed my filter without asking me) I decided to run some Valvoline Synpower 5W-30. Wouldnt you know it my mileage went up to 17 mpg's. According to everything Ive read Amsoil is the better oil (at least numbers wise), so why would my mileage increase with an "inferior" oil? [ September 14, 2003, 01:38 PM: Message edited by: Jason8691 ]

 

[Al]

I would bet the farm the difference is from other factors. The Amsoil may be slightly thicker and that could make a slight difference. Also the Valvoline could shear back (get thinner) as you drive. But 17 compared to 15 is 13.3%. That is just not possible .the fact that you mentioned exactly 15 mpg and 17 mpg shows (possibly) that you may not have been accurate or careful in your calculations. Also if you don't check milage over many tankfulls an similar conditions there are huge inaccuracies. This is not a slam on you its just a thought as to why the difference. Like I said its just not possible. [ September 14, 2003, 01:49 PM: Message edited by: Al ]

 

[Jason8691]

It is possible, I may not have gotten as much gas in the tank or whatever. I try to keep accurate data on this because my truck is a gas hog! But either way, mileage did increase.

 

[Mike_dup1]

Oil cannot contribute the that much of an increase in mileage. Why was it in the dealer? Can't be for the oil change because they caught you by surprise with that. That may explain it, but I cannot believe it the oil. btw I have a Friend with the exact same truck, we both have 2001, mine a GMC and his a Chevy. Everything else is exactly the same except for the paint and interior. He claims he gets 22 mpg yet the very best I can do it 17 averaged over 1000 miles. The window stickers list the mileage range of 13-18. In talking with him one day, I found out how he gets the good mileage. He only checks one tank and only when he goes on some trip. If he gets 22 then, he assumes he gets 22 all the time. He see's no point in averaging the fuel used over a longer span of miles, say 1000+. [ September 14, 2003, 03:58 PM: Message edited by: Mike ]

 

[Jason8691]

It was at the dealer to get oil cooler seals replaced. The mechanic claimed it was the oil filter that was leaking (even tho there was no oil on the filter, but there was on the cooler lines), so he replaced it along with changing my oil ( I know its common practice to dealers to do the simple fix first to shut the customer up). So I filled up again today, my mileage for this tank was 16.5. I cant explain it, I have no idea why there is the increase that there is. But its there. All of my previous tanks were at the high 14's, and low 15's. I had one tank that went to 17.I. I havent changed driving habits, the weather is still hot, I didnt use a higher octane gas. I dunno, thats why I posted this cause oil shouldnt make that big of a difference. [ September 14, 2003, 04:04 PM: Message edited by: Jason8691 ]

 

[Robbie Alexander]

quote:

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Originally posted by Jason8691: --snip-- So I filled up again today, my mileage for this tank was 16.5. I cant explain it, I have no idea why there is the increase that there is. But its there. All of my previous tanks were at the high 14's, and low 15's. I had one tank that went to 17.I. I havent changed driving habits, the weather is still hot, I didnt use a higher octane gas. --snip--

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Don't worry "Be Happy" Hey, unless you keep detailed records over lots of miles, sometimes it can look like you are getting poor MPG or better than you are. Did you change stations? Maybe the station changed fuel jobbers, or a new plant is selling the jobber his fuel, maybe you are lucky enough to have a station that has treated gas. There are also jobbers cheating the stations, and perhaps they were audited, or found out... Did you change tires or anything??? Oil can increase 1-4-6% on fuel and fuel additives can increase 1-7% on MPG. The rest of the increase could be the auto getting more broke in, or perhaps, the computer adjusted itself, could be a lot of things... Keep a log! Mine looks like it varies UP CLOSE i.e. 23.65,24.12,24.90,23.08,21.93, 22.34,22.64,24.58,24.31 (some of these numbers are for 6 gal and others are for 14 gal) keep teack 3-8 places and add the total amount of fuel pumped and the total miles traveled to get the larger view. Just like oil testing, the numbers on MPG CAN change.

 

[Jason8691]

Robbie-No, didnt change tires, but I do use different gas stations. I like to try to stick to the same station for consistency, but sometimes their prices are alot higher than other stations and I go for cheaper. I was getting my worst mileage in the heat with the AC on, but I dont count that. Its been the last 4 tanks where I have noticed the difference.

 

[crashz]

Did the dealer re-set the computer (by disconnecting the battery)? This will change all of the parameters and set them to factory defaults. Then the computer will re-learn what it thinks is the proper settings. Sometimes this will affect mileage.

 

[Jason8691]

I dont think they did. All my radio settings were the same when I got it back. Unless GM has devised a way to store that stuff when the battery is disconnected. [ September 16, 2003, 06:23 PM: Message edited by: Jason8691 ]

 

[labman]

You can reeset the computer by pulling the ECM fuse without reseting the radio.

 

[Robbie Alexander]

quote:

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Originally posted by Jason8691: Its been the last 4 tanks where I have noticed the difference.

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yeah, I wouldnt count 4 tanks, maybe 20 or 40 but not four. Hey the good news though, maybe it's like my Taco, Ever since I got it when new (about 143 miles) it has gotten better and better MPG. IT goes up and back down a little then hangs for awhile (20-30-40K) then goes up again, partly back down some and then hangs again (20-40K) then repeats. I thought it was over recently, but I think I may have noticed a slight increase again, anyhow, it's taking longer and longer between increases, I may never get another.

 

[Robbie Alexander]

quote:

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Originally posted by labman: You can reeset the computer by pulling the ECM fuse without reseting the radio.

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Does anyone know why the milage always goes up for a short while after this is done, before returning to the """normal""" Although a few times I have had worse MPG, most often this is not the case. Also when my truck was new I was getting super power and MPG until I took it to the dealer to service a Check Engine light ( about the 3rd day or maybe 1st week), then everything kinda peter-ed-out, and been many a bad MPG and HP days.