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Old 10-22-2009, 09:54 PM   #1
mattymx
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Default big hit in MPG after switching oil brand

So I have been reading how a lot of people like the Rotella synthetic 5-40 for the WRX. I have been running that oil in my 2 Ford Powerstroke diesels for years and love it.

The first oil change I did on the car from new was at 1700 miles and I ran Pennzoil Platinum and the car loved it and have ran that oil ever since, until this last change 2 weeks ago. I do a lot of freeway driving and usually get around 28MPG on the "B" trip meter that I use for oil service intervals. For the life of me I cant get to 25MPG now after the switch to Rotella. Same driving habbits and same gas station.

Anyone else see a drastic drop in MGP after switching oil? I might just change back to Pennziol in a week or so.
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Old 10-22-2009, 10:10 PM   #2
sLicK 2004
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Im interested in info on this as well. I've been looking to switch to that oil too
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Old 10-22-2009, 10:39 PM   #3
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Wirelessly posted (Opera/9.80 (J2ME/MIDP; Opera Mini/4.2.14320/812; U; en) Presto/2.2.0)

switched from GC 0w30 to rotella 5w40, no change in mpg at all.
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Old 10-22-2009, 10:53 PM   #4
sLicK 2004
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You plan to stay Rotella year round?
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Old 10-22-2009, 10:54 PM   #5
mattymx
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Originally Posted by nhat View Post
Wirelessly posted (Opera/9.80 (J2ME/MIDP; Opera Mini/4.2.14320/812; U; en) Presto/2.2.0)

switched from GC 0w30 to rotella 5w40, no change in mpg at all.
Interesting...
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Old 10-22-2009, 10:57 PM   #6
mattymx
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You plan to stay Rotella year round?

I am not going to run it in the full of winter because where I live it gets close to 0* for a few months. but I usually have 10 gallons in my garage for my trucks so I thought I would try it before winter starts. Car seems to run great but the MPG sais no.
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Old 10-22-2009, 11:26 PM   #7
sLicK 2004
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Gc 0w-30 for winter?... im thinkin about switching over from conventional and ive just heard alot of good things about rotella in the spring summer fall and GC in the winter
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Old 10-22-2009, 11:39 PM   #8
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Quote:
Originally Posted by sLicK 2004 View Post
Gc 0w-30 for winter?... im thinkin about switching over from conventional and ive just heard alot of good things about rotella in the spring summer fall and GC in the winter
the above is proof that the poster does not know what those funny little numbers that come on oil bottles mean

along with about 90% of all other board members


this is not rocket science and 5w40 can be used anywhere south of the ****ing arctic circle and changing it for winter is ****ing ridiculous for all but a handful---litterally.... of board members
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Old 10-23-2009, 06:34 AM   #9
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Originally Posted by mattymx View Post
I am not going to run it in the full of winter because where I live it gets close to 0* for a few months. ...
The owner's manual says that you can run 10W-40 from around 0F and higher. The first number on a bottle of oil is a winter rating, but not actually the lowest temperature at which you can run the oil.

-Dennis
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Old 10-23-2009, 09:53 AM   #10
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i'm using rotella 5w40 for the rest of my car's life...
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Old 10-23-2009, 09:57 AM   #11
sLicK 2004
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i'm using rotella 5w40 for the rest of my car's life...

I just I've just decided to do the same=)
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Old 10-23-2009, 10:45 AM   #12
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Is there a chance your area has switched to winter blend gas at this point?
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Old 10-23-2009, 11:10 AM   #13
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cheers to winter blend, or them changing to E10.... my MPg tanked when my station changed to E10... found a better station that advertises 100% ethenol free and back to 26MPG. I used to use Q power 5w30, changed to the rotella synthetic 5w40 and no change...

kinda a long shot, but is it possible you just really overfilled the oil and now its just a lot more drag on the engine?

T
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Old 10-23-2009, 11:28 AM   #14
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Originally Posted by DrnknZag View Post
Is there a chance your area has switched to winter blend gas at this point?
+1 You beat me to it.
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Old 10-24-2009, 12:54 PM   #15
mattymx
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Originally Posted by DrnknZag View Post
Is there a chance your area has switched to winter blend gas at this point?

I doubt it. the station I fill up at is in Los Angeles so I dont think they are going to use winter blended fuel. Oh and I do know what the numbers on oil mean.. It's not that I dont think the rotella cant handle the cold, but the fact that I have 2 more changes of 0w30 Platinum I want to get rid of.

One thing to note on this. My friend drives a modded LS1 Camaro and fills up at the same station. He noticed his car is runnign a little rough and down on power. I wonder if they fueled the wrong tanks with 87 and 91. Im going to fill up at a different station and see if it was the fuel.
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Old 10-24-2009, 01:10 PM   #16
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Quote:
Originally Posted by Uncle Scotty View Post
the above is proof that the poster does not know what those funny little numbers that come on oil bottles mean

along with about 90% of all other board members


this is not rocket science and 5w40 can be used anywhere south of the ****ing arctic circle and changing it for winter is ****ing ridiculous for all but a handful---litterally.... of board members

What he said

I switched from a free-dealer-fill of Cam2 5W/30 with a 100C of around 8.5 cst to RTS 5W/40 with a 100C of around 12.8 cst - all numbers according to UOA, not PDS info.

Fuel economy has increased over the past two oil changes using RTS. Cold flow properties of most group III oils are very similar. PP and RTS are pretty similar regardless of the difference between the XW label. The major difference is the RTS having a high flash point and high viscosity at operating temp.
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Old 10-24-2009, 02:15 PM   #17
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temps are cooler these days as well. so if you're doing your trips in the mornings/evenings, you will see lower MPG. I drive 800 miles/week and noticed cooler morning air dropping my mpg by a few.
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Old 10-25-2009, 01:20 PM   #18
mattymx
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Originally Posted by Tahoe SC View Post
temps are cooler these days as well. so if you're doing your trips in the mornings/evenings, you will see lower MPG. I drive 800 miles/week and noticed cooler morning air dropping my mpg by a few.


I dont think that is it becasue the temps have been in the 90's and hotter the last 2 weeks. I filled up at a different station so I hope I just got some crap fuel.
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Old 10-25-2009, 02:47 PM   #19
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Quote:
Originally Posted by mattymx View Post
One thing to note on this. My friend drives a modded LS1 Camaro and fills up at the same station. He noticed his car is running a little rough and down on power. I wonder if they fueled the wrong tanks with 87 and 91. I'm going to fill up at a different station and see if it was the fuel.
Keep in mind, one tank of gas is not much of a clue to how the mileage is doing. A minor change in when the fuel pumps shuts off (changing the quantity of fuel added) can make a big difference in "achieved mileage".
In the same vein, a minor change in your driving (a couple of hard "stop light launches") can also affect your mileage over one tank of gas.

Checking the mileage over a few tanks of gas would be better.
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Old 10-25-2009, 04:43 PM   #20
mattymx
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I know what you are saying, but I do hand calculate every tank when I fill up at the same station using the same pump. the oil is really the only thing that has changed with the 2 tanks used since then. I just filled up from a different station and the WRX's trip meter is right where it used to be so far. I will calculate it by hand the next fill up and see what it reads.
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Old 10-25-2009, 10:44 PM   #21
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It may be gas blend. I live in Florida and the past two weeks by MPG has TANKED also!!! I'm barely getting 20 mpg in my STi when I used to average almost 22 for a tank. Oh and I'm running the same oil too, Rotella 5w40.

Paul
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Old 10-26-2009, 03:02 AM   #22
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Well I saw a pretty drastic rise in mpg after switching from 10w30 to 5w30 oil. Went from 24mpg to 27.

Isn't that first number supposed to be the viscosity of the oil when cold, with the second being the viscosity when hot? What I mean is, if you went from a 30 weight to a 40 weight, wtf did you think was gonna happen with the mpgs?
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Old 10-26-2009, 10:25 AM   #23
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Originally Posted by bomber991 View Post
Well I saw a pretty drastic rise in mpg after switching from 10w30 to 5w30 oil. Went from 24mpg to 27.

Isn't that first number supposed to be the viscosity of the oil when cold, with the second being the viscosity when hot? What I mean is, if you went from a 30 weight to a 40 weight, wtf did you think was gonna happen with the mpgs?
The first number isn't really a weight; it pertains to the cold-flow characteristics. The second number represents an actual range of viscosities at 100C - the higher the number the thicker the oil will be at operating temperature.

Unless you do a lot of short-trip driving where in the oil never gets up to temp I doubt you gained 12.5% in mileage due to switching from a 30 to a 30. Even short-trip only driving wouldn't realize 12.5% IMHO...
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Old 10-26-2009, 10:32 AM   #24
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Originally Posted by bomber991 View Post
Well I saw a pretty drastic rise in mpg after switching from 10w30 to 5w30 oil. Went from 24mpg to 27.

Isn't that first number supposed to be the viscosity of the oil when cold, with the second being the viscosity when hot?
Not really, the first number indicates that the oil has passed a certain low temperature pumping and cranking viscosity test at a certain temperature as shown in this graphic:
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Old 10-26-2009, 12:46 PM   #25
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Quote:
Originally Posted by bomber991 View Post
Well I saw a pretty drastic rise in mpg after switching from 10w30 to 5w30 oil. Went from 24mpg to 27.

Isn't that first number supposed to be the viscosity of the oil when cold, with the second being the viscosity when hot? What I mean is, if you went from a 30 weight to a 40 weight, wtf did you think was gonna happen with the mpgs?
Yes and no. It could be a 5, but it depends on the temp. Its going to be different from 40 degrees to 10 degrees.

And yes higher viscosity oils, will cause lower MPG. Its simple physics, you cant do more work (pumping oil with a higher resistance to flow) without using more power (which ends up as fuel). However there usually isnt a noticeable difference....but the owners manual clearly states that lower viscosity oils get you better MPG, higher viscosity oils get you better engine protection.
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