GC 0W-30 hit in gas mileage

[metroplex]

I keep tight records of my gasoline transactions and noticed a significant decrease in city driving gas mileage. Standard average was about 14.5-15.5 mpg but consistently above 15 mpg.

Now, the best I'm getting is about 14.5 mpg. I noticed that this started to occur after I switched to Castrol Syntec 0W-30 (GC). Has anyone else noticed the same thing?

The only other explanation is that my car gets better gas mileage in the winter (-10F to 20F) versus 50F-80F ambient with some spikes into 80F-100F in the summer.

Car is a 2000 Ford Crown Vic.

 

[Islandvic]

It's the A/C on Max all the time bro.

I'm taking a hit too in my Panthers also, just like my electricity bill for my house!

The GC bug hit ya huh?

 

[AndyH]

And what brand & weight of oil did you run prior to the GC?

 

[Gary Allan]

Fuel economy is a short trip thing in regard to the differences in visc. If you did mainly highway you wouldn't notice a thing, IMHO.

 

[metroplex]

I was using Mobil 1 5W-30 prior to GC 0W-30.

My driving style and pattern stayed the same. It's 100% city driving. Again I keep tight records of my fuel consumption and I can give you figures from the day I purchased the vehicle.
There's a definite 1-2 mpg loss after I used GC 0W-30.

I've only had the GC 0W-30 for about 3 months and there's a large possibility it's the A/C, but last year around the same time, I was getting 15.2-15.5 mpg easily w/ the A/C.

 

[jsharp]

I thought I'd seen some MPG loss with GC but I also had purchased new tires about the time I started running it. I've since run some other oils and seen lower mileage with them also. If there is a difference between GC and a thinner 0W-30, it's hardly possible to measure it in my application...

 

[MNgopher]

I too keep meticulous fuel mileage records and I noticed a very definite drop in fuel mileage in my '99 F150 with the 4.6 using 5w40 oil versus 5w30 or 5w20. I measured it to be nearly a 5% hit, on a year around basis.

Given that GC is a thick 30, I'm not terribly surprised at a drop in fuel mileage, especially compared to M1, which has always been on the "thin" side of a 30.

I suspect the mod motors are one that actually does note a fuel mileage hit on thicker oils. I will note my UOA's did not show a major difference between thick and thin, but the thicker UOA's were slightly better (emphasis on the slightly!).

 

[bulwnkl]

Like Ray H said, it's amazing how you don't get something for nothing (although you often get nothing for something).

 

[metroplex]

Interesting MN Gopher!
I have a large supply of the GC 0W-30, so I guess I'll have to suck it up and take the gas mileage hit like man until I switch back to a lighter 30 oil.

 

[Islandvic]

That sucks if its the GC.

 

[Ray H]

Metroplex, you'll note on the GC 0W-30 bottles that the oil's NOT rated as "Energy Conserving". GC is a "thicker" than usual 30 weight when hot. Lower fuel mileage or enhanced film strength - it's always a trade-off. At worst, you're still only "suffering" a single digit percentage drop anyway.

 

[metroplex]

You're right Ray. It's about 1-2 mpg max, nothing to write home about but I was wondering if the GC was the culprit or if I was somehow losing gas mileage elsewhere.

 

[Ray H]

I can't rule out the second possibility from 1,500 miles away (might still wanna check your tire pressures, though), but given that the fuel economy drop occurred immediately after switching to GC, I strongly suspect the GC. For what it's worth, I'm fundementally too cheap to use any motor oil priced over a buck and a half a quart, but, if I ever succumbed to the temptation to pop for a full synthetic, it'd probably be GC.

 

[mechtech]

GC is a real thick 30W.
Hence more drag.

 

[Ugly3]

Not only is GC a thick 30w at operating temps it is also a thick oil at lower temps until you get to something like -20F. I am not surprised at a small loss in MPG when the vast majority of miles are not pure hiway miles.

Hopefully you are getting the low wear rates that GC has produced in most applications.

I have 40 some quarts of GC for use in my wife's Buick 3100 V6. The MPGs are pretty good in general so I am not too concerned about losing a few, looking for the low wear.

 

[lyle]

I took two trips up to the in-laws lake place around Memorial day, one trip was 459 total miles, the other was 463 total miles. Running a 50/50 Motorcraft 5W-20/5W-30 brew I averaged 15.6/15.7 mpg. This is in a '98 5.4L Expedition. I'm doing the exact same trip in a few hours. Since I switched to GC 3 days ago, I'm curious to see what mpg hit I will take, if any. I'll try to report back, but it'll be a few days.

 

[blupupher]

My mileage has been about the same with factory fill, Mobil Drive Clean 10w-30, GC, and Royal Purple 10w-30.
The biggest difference I notice is the summer/winter gas switch. 2-3 mpg drop with winter blend gas.

 

[TooSlick]

No surprise ...Mobil 1 is much thinner at operating temps....

TS

 

[lyle]

quote:

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I'll try to report back, but it'll be a few days.

---

Well, results are in with my GC trip. 561 miles total driven using 37.5 gallons of gas, that's close enough to 15.0 mpg to call it even. Driving conditions were the same, no A/C usage, freeway for most of the trip at 75mph. Compared to my earlier MC runs, I'd say there is about a 5% hit using GC. I can live with that.