GC vs. M1 MPG in GM 3800

[lght11]

Hi

I have used M1 10w-30 for the last 100k, but have recently changed to 0w-30 GC to try.

Since changing last Monday, and having gone about 1100 miles, I have noticed mpg to be somewhat lower than I am accustomed to, say about 2-3 mpg.

How does my observations compare to others using GC?

If, over the next 6k miles, the miles dont come back up, I will switch back to M1, possibly using 5w-30 for the winter.

I keep accurate fuel consumption record each day, so I have a good way to spot trends.

 

[pitzel]

How much has the temperature changed?

My real time MPG readings have taken a serious turn for the worse recently just with the change of temperature here, so if I were you, I wouldn't be so quick to discount both the effects of temperature as well as the effects of petrol formulated for winter operations.

 

[mechtech]

2-3 MPG is a lot of change, esp. from just using different oils of very similar weights. Something else is a contributing factor.

 

[michaelc80]

I'd do more long term testing-there could be other factors involved. 1100 miles is only 2-3 tanks of fuel.

Like pitzel said, cold can affect the mileage significantly, and I think I would at least run it until you have some warm weather mileage to compare it to.

 

[JHZR2]

there has to be a difference considering the visosity at temp of the GC is higher than the M1. Youre bound to see some effect, IMO. 2-3MPG is a bit high, 0.5-1 mpg would be more like it.

Are you sure your gas stations didnt just start selling oxygenated fuel for the winter? That can make a drop that large be realized.

JMH

 

[Patman]

I saw no drastic change in MPG when switching my wife's Honda over to GC, and the same thing with my previous car.

I switched my Corvette over as soon as I got it, so I have no data on previous oils. I will say that I do get pretty decent gas mileage though, I average 21.0 to 21.5 MPG in my daily commute (which includes some brutal rush hour traffic) and have been able to get 27.5 MPG on longer highway trips at a steady 70mph. This is with the performance axle ratio too (3.15) which means if I had the standard ratio (2.73) it would get 2-3 MPG more on the highway (and possibly 0.5 to 1.0 more in the city)

 

[haley10]

My 3800 Series II likes GC and I have seen no mpg drop from when I used M1 10W-30.

I'd stick with the GC for awhile and see if you can rule out the possibility of "Winter" gas formulation coming into play. Your location makes me think this could be a factor.

M1 10W-30 did work well for me. I'm thinking GC may be the ideal for this engine, but I have yet to prove it. I tried Syntec 10W-40 (very light 40wt.) in warm weather and my fuel economy did go down and the engine didn't feel as peppy. I figure GC is just about right.

[ December 09, 2004, 01:42 PM: Message edited by: haley10 ]

 

[lght11]

hi

i have accurate records going back years for this car, so i can compare any day, week, month..etc.

also, i use the same gas station, and the change in mpg was almost immediate. fwiw, i gas up each day..so i do have some data to analyze.

as for the temps, no big change from one week to another, so "seasonal adjustments" are out of the question.

i was getting 25-27 mpg per tankful consistently with M1 immediately before GC. Since GC, each tankful (top off EVERY DAY ) now yields 22-25, with one at 20. Needless to say, this has caught my attention.

as for the "winter formulation", this is december and the changed occured several months ago. My drop in mpg occured exactly when GC went in.

i'll give this oil until the final week of Dec to prove itself, and if it doesnt, M1 goes back in.

 

[haley10]

lght 11, that seems unusual. My gas mileage is good enough, that I don't religiously keep records or anything. Gasoline is kind of a generic product and stations do switch suppliers. You might ask the manager if anything is different there? No matter, M1 works well. It will be interesting to see if you go back if the mileage immediately goes back up.

 

[Spector]

I am on my second 3800 Series II engine both 2000 models and both SC. Previous one and this one use Amsoil 10W30 and highway mileage is consistently 30-32 mpg (I can get 33-34 if I don't make rest stops and there are no accidents/construction etc) and around town I am at 22-24 mpg consistently. I expect to see lower in winter on all cars as well.

I seriously doubt it is the oil if you are seeing a diff!

 

[lght11]

hi

i keep track of this as it is a major expense. i drive about 1100-1250 miles a week and the miles and dollars add up quick.

i have used another gas in another city, and the miles on that is poor as well.

there are no other factors to consider, other than the oil as that is the only thing that has changed.

also, i just compared records for january 2004, which was our coldest month, and the GC mileage is beneath those of the coldest days.

 

[gogozy]

i had same feeling that GC worsen mpg on my TSX as well. i do not have rigous loggin as lgt11 but i calculate most fill up and big changes catch my eyes. GC drop 1-1.5mpg at first and then slowly improve-but improve can be attributed to summer weather. i was using GTX before GC, i will switch to M1 5w-30 next week or 2 and Esso XD3 0W-30 in summer. lgt11, keep tracking, and MPG on GC may improve later.

 

[haley10]

quote:

---

Originally posted by lght11:
hi

i keep track of this as it is a major expense. i drive about 1100-1250 miles a week and the miles and dollars add up quick.

i have used another gas in another city, and the miles on that is poor as well.

there are no other factors to consider, other than the oil as that is the only thing that has changed.

also, i just compared records for january 2004, which was our coldest month, and the GC mileage is beneath those of the coldest days.

---

Can't argue. That's racking up some mileage. What kind of oci's are you doing on the M1?? That's got to be a lotta highway mileage. A little LC might be an advantage for you if extended oci's are desired. I think M1 5 and 10-30 can benefit from it. M1 0W-40 could do extended drains on it's own and hold up well. It has the starburst (GC doesn't). I think it's a little much viscosity-wise, but might also be worth a try.

If I weren't a bitog guy I would have just settled on M1 5-30 and 10-30 forever, but that would be no fun. This is an ideal engine to try Amsoil in for some slightly extended drains also.

 

[lght11]

hi

i change every 6k, mostly due to some piece of mind on having the chance to grease the fittings and observe the car myself.

i do a filter change at 3k.

since may '03, i've driven almost 82k.

i replaced the rear valve cover gasket recently, and it look spotless inside, so M1 is good stuff.

the car had dino GM @3k until i bought the car, and since..it has been on 10w-30 M1 until now.

 

[haley10]

quote:

---

Originally posted by lght11:
hi

i change every 6k, mostly due to some piece of mind on having the chance to grease the fittings and observe the car myself.

i do a filter change at 3k.

since may '03, i've driven almost 82k.

i replaced the rear valve cover gasket recently, and it look spotless inside, so M1 is good stuff.

the car had dino GM @3k until i bought the car, and since..it has been on 10w-30 M1 until now.

---

Do you think the filter change at 3K is necessary. I don't. Your probably adding 1/2 quart top up oil anyway. Any good filter should make 6K alright.

 

[Hirev]

quote:

---

Originally posted by lght11:
Hi

I have used M1 10w-30 for the last 100k, but have recently changed to 0w-30 GC to try.

Since changing last Monday, and having gone about 1100 miles, I have noticed mpg to be somewhat lower than I am accustomed to, say about 2-3 mpg.

How does my observations compare to others using GC?

If, over the next 6k miles, the miles dont come back up, I will switch back to M1, possibly using 5w-30 for the winter.

I keep accurate fuel consumption record each day, so I have a good way to spot trends.

---

It would not surprise me. My truck that I owned many years and used many oils in see up to 1 1/2 mpg difference between different oils. The strangest thing is heaver oils do better in it. I think because of ring seal. HDEO in the 15w 40 always seem to do the best MPG. 5w 30 dino oils the worst MPG. It does not seem to be a brand thing for me it seems to be a oil weight problem.

 

[Last_Z]

quote:

---

Originally posted by lght11:
Hi

I have used M1 10w-30 for the last 100k, but have recently changed to 0w-30 GC to try.

Since changing last Monday, and having gone about 1100 miles, I have noticed mpg to be somewhat lower than I am accustomed to, say about 2-3 mpg.

How does my observations compare to others using GC?

If, over the next 6k miles, the miles dont come back up, I will switch back to M1, possibly using 5w-30 for the winter.

I keep accurate fuel consumption record each day, so I have a good way to spot trends.

---

My wife noticed a "big drop" in gas mileage with GC (which is still in use.)
Now, for my wife to notice a drop in MPG's, it must've been big because she is 99.9% car clueless!
Could be wrong, but she mentioned something like 25-40 less miles per tank.

 

[Spector]

You can easily go 7500 on this engine, it is easy on oil. My previous 3800 I went 12,000 mile OCI and on my current one I just received a 7600 mile UOA back and it was great. these engines, especially on the highway, with 70 mph the RPMS around 2000, are very easy on the oil!!

 

[Dominic]

That's good to know. I plan on increasing my OCIs and running valvoline synpower to do it. I get very good fuel economy on valvoline oils and M1 on my 3800 Camaro manual... Why did you switch from M1?

 

[PaJohn]

In my Audi S4, my onboard computer has been showing an average mpg of 20.0 with GC when it used to show 22.0 or so with Amsoil 0W30. I know these computers are notoriously inaccurate, and I can't rule out other possible causes, so i'm not about to completely blame the GC. But it is interesting to note that you notice a similar drop.