Different weight/brand oil helps MPG?

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Clermont, Florida
I am trying to improve the MPG in my Dakota and I wonder if there is any oil out there that can make a noticeable improvement MPG? It's a V6 3.9 liter engine, manual 5 speed transmission and I have owned it since 42,000 miles. From 42K to 65K I used Valvoline conventional. At 65K I changed over to Maxlife and recently did a couple of OC's with Napa brand HM, all were/are 10W30. I just wonder if anyone else has had any real MPG gain from changing to other brands and/or weights?
 
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One weight lower from 10W30 to 5W20 or thinner oil may improve gas mileage by a small percentage 1-3%. Peak oil xW30 is very thin, almost as thin as 5W20.
 
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If you're doing mostly short stuff, a lower visc may save you some nickles. If you're doing longer stuff, I doubt you would notice. Do the diff and trans with a synth if they're due.
 

Jimmy9190

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Clermont, Florida
Why would you say Maxlife is not good for MPG? I use a synthetic gear oil in the transmsission already, Pennzoil Synchromesh. It or the Mopar fluid is the only lube I can use in it. I use Valvoline 75W90 conventional gear oil in the rear end. At the next change for it I plan to use Valvoline synth 75w90 so I won't have to change it so often. I calculated my MPG from my last 2 fuel fill-ups and it's about 20.5, which I guess is pretty good for a 3000 pound truck that is underpowered with a 175 hp engine. I know of others with the same truck are getting way less MPG, around 14 or 15 MPG. But who knows what shape they are in and what the driving conditions are. I'm really just curious to see if a different oil would help me improve my own MPG. I'm also curious and a little anxious about what kind of prices we will see for gas this summer. I am trying to get all the miles I can from the gas I buy. Thanks for the help.
 
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From what Ive experienced, stick with a synthetic at the lower end of the viscosity scale at 100 deg. C And change the diffs our with 75w90 syn if its allowed. My Jeep gave me the option to run 75w140 or 75w90 dependig on the use. 75w90 made more of a difference than the engine oil change. Also, like what was mentioned before, syn tranny fluid might help as well.
 
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Vermont
 Originally Posted By: Jimmy9190
I am trying to improve the MPG in my Dakota and I wonder if there is any oil out there that can make a noticeable improvement MPG? It's a V6 3.9 liter engine, manual 5 speed transmission and I have owned it since 42,000 miles. From 42K to 65K I used Valvoline conventional. At 65K I changed over to Maxlife and recently did a couple of OC's with Napa brand HM, all were/are 10W30. I just wonder if anyone else has had any real MPG gain from changing to other brands and/or weights?
20 MPG is not bad for a Dodge truck. IMO, oil brand or viscosity changes will affect gas mileage much less than driving habits. I suspect that your driving style already enhances your fuel economy but there is a limit to what you can get out of your truck. I run the [censored] out of our '02 civic with frequent redline runs and still average 35+ mpg.
 
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Consider an electric fan conversion. I had a 92 3.9 and the fan sounded like a school bus at times and I could really feel the drag. OTOH I think that truck flew and I only had 3.2 gears!! I think if you find it slow you may be something of a lead foot. I had a dakota 2.5 as well and that tempered any speed demon influence. Both good trucks, I like the pre 97 body style. Agree on the rear end and tranny oil ideas. Here's a thought, drive it home so everything gets all good and hot. Park in a perfectly level spot. Put it in neutral, get your bathroom scale, push on the scale against the tailgate and record that # of lbs as its rolling resistance. Do the same in the morning when it's cold. Change the oil and diff fluid and repeat, you'll have four data points to tell you if it was worth it.
 

Jimmy9190

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3,653
Location
Clermont, Florida
I agree, I think my truck is doing as well as it can on gas. I just wondered if different oils or different viscosities might improve mpg. I read an online article yesterday about how changing from 10W40 to 5W30 can improve mpg and it got me thinking about other viscosities and oil brands.
 
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Peterborough
 Originally Posted By: Jimmy9190
I agree, I think my truck is doing as well as it can on gas. I just wondered if different oils or different viscosities might improve mpg. I read an online article yesterday about how changing from 10W40 to 5W30 can improve mpg and it got me thinking about other viscosities and oil brands.
Now going from 10w40 to 5w30 I could see making some difference.
 
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Pensacola & Vero Beach FL
 Originally Posted By: Jimmy9190
Why would you say Maxlife is not good for MPG? I use a synthetic gear oil in the transmsission already, Pennzoil Synchromesh. It or the Mopar fluid is the only lube I can use in it. I use Valvoline 75W90 conventional gear oil in the rear end. At the next change for it I plan to use Valvoline synth 75w90 so I won't have to change it so often. I calculated my MPG from my last 2 fuel fill-ups and it's about 20.5, which I guess is pretty good for a 3000 pound truck that is underpowered with a 175 hp engine. I know of others with the same truck are getting way less MPG, around 14 or 15 MPG. But who knows what shape they are in and what the driving conditions are. I'm really just curious to see if a different oil would help me improve my own MPG. I'm also curious and a little anxious about what kind of prices we will see for gas this summer. I am trying to get all the miles I can from the gas I buy. Thanks for the help.
Because the Maxlife grades tend to be at the high end of the viscosity range for the grade in question. It's just part of the equation for high-mileage oils (but not the only factor, of course). Interestingly enough (I think...), I just this weekend changed the oil in my Camry Hybrid, and based upon language in the manual, decided to try some of my old green GC (a thick 30) instead of the normally recommended xw-20 oils (see the thread I started today). Not too surprisingly, my mpgs are down by at least two or three.
 

Jimmy9190

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3,653
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Clermont, Florida
Thanks, I had not really considered Maxlife might be detrimental to MPG because it is thicker. It does make sense though. I had always considered Maxlife to be a very good robust oil, especially after reading about it here on BITOG. I am doing an OC this weekend and I might just use a regular 10W30 instead of Maxlife or Napa HM. I'll probably use the Napa brand 10W30 and see if I get any better MPG. I have found the Napa oils are every bit as good as Valvoline brand, they just don't cost as much. Thanks again.
 
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