Does higher cSt number = lower fuel economy?

[ringmaster]

I am nearing the end of my engine break-in period and want to switch from Pennzoil 5W30 to a synthetic oil. The oil I plan to use is Esso XD-3 0W30 or Motul 8100 0W40.

My question is, will a thicker oil (as determined by the cSt number) increase my fuel consumption compared with a thinner oil? Will it reduce power output? Do the benefits of a full-synthetic oil have any effect on this?

Pennzoil 5W30
cSt @ 40C: 64
cSt @ 100C: 10.5

Esso XD-3 0W30
cSt @ 40C: 71
cSt @ 100C: 12.1

Motul 8100 0W40
cSt @ 40C: 73
cSt @ 100C: 13.3

Thanks for your help

 

[Al]

Well normally a change from a 30 wt to 40 wt could be say 3% or so but the difference between XD-3 and Motul won't have much difference (if any) in economy. Little difference between syn/dino on economy or power from what I have seen, read, experienced. There will be other opinions though.

 

[Shannow]

Over the last 35,000km, I've had the following.

code:

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9.9cst dino 10.90km/l

15.8cst dino 10.25km/l

14.3cst synth 10.70km/l

12.9cst synth 10.22km/l

14.4cst GRIII 10.80km/l

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The shock to me was using the 40 that was nearly a 30, and getting the same mileage as a thick dino.

I think that the add packages mean more than even a 4 cst change in viscosity.

 

[The Critic]

It depends. On old engines that are worn out, thicker oil will provide better ring seal, as a result, perhaps an increase in compression which may lead to better fuel efficiency.

On new engines, the answer is no. However, the fuel economy loss, if any, is quite dependent on the type of service the vehicle is used for. Short trips in which the oil does not warm up, will notice a greater drop in fuel efficiency with thicker oil as the oil will be significantly thicker. With prolonged highway driving, the oil will be warmed up and the viscosity difference between the grades isn't that much, so any fuel economy loss may not be as noticeable.

Mike

 

[Bob Miller]

The penzoil looks pretty good to me for the winter...

Because of the number of variables by car/driver/conditions, about all you can do is try each and keep good records.

 

[Blue99]

At most, Esso XD-3 0W30 will generate a 1-3% gas mileage penalty.

During cold winter temperatures, XD-3 0W-30 may even provide slightly better fuel economy during the 10-15 minutes required to for the crankcase oil to reach full operating temperature.

 

[Palut]

quote:

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Originally posted by Michael Wan:
It depends. On old engines that are worn out, thicker oil will provide better ring seal, as a result, perhaps an increase in compression which may lead to better fuel efficiency.

On new engines, the answer is no. However, the fuel economy loss, if any, is quite dependent on the type of service the vehicle is used for. Short trips in which the oil does not warm up, will notice a greater drop in fuel efficiency with thicker oil as the oil will be significantly thicker. With prolonged highway driving, the oil will be warmed up and the viscosity difference between the grades isn't that much, so any fuel economy loss may not be as noticeable.

Mike

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Well spoken. I agree completely.

 

[ringmaster]

quote:

---

Originally posted by Blue99:
At most, Esso XD-3 0W30 will generate a 1-3% gas mileage penalty.

During cold winter temperatures, XD-3 0W-30 may even provide slightly better fuel economy during the 10-15 minutes required to for the crankcase oil to reach full operating temperature.

---

Thank you to everyone who has replied. My car is a 2005 with >10k.

The above information is of interest to me. Since the cSt # is only give for 40C I have always wondered how one can know the viscosity at, say -20C, 0C, 20C, etc, as this will no doubt have an effect on how the engine runs and the economy it will generate during the warm-up phase. I did notice that the Pennzoil 5W30 has a pour point of -36C while the XD-3 shows -48C, but this is perhaps more to do with dino vs. synth than the viscosity?

Thoughts?

 

[Blue99]

Here, I'll help you provide the viscosity data to answer to your question.

See the viscosity calculator in This Link .

Work with module #4.

Fill in the data for XD 0W-30:

Temp 1 = 100
Vis 1 = 12.1
VI = 168
Temp of Interest = (Whatever temp in C you wish to view)

So you can build a chart to compare the viscosity of 2 or more oils at the colder temperatures.

A good method of learning how thick your favorite oil is at a variety of temperatures!

 

[boxcartommie22]

both of those cst's are 30 wt. motul is a high 30wt...

 

[ringmaster]

quote:

---

Originally posted by Blue99:
Here, I'll help you provide the viscosity data to answer to your question.

See the viscosity calculator in This Link .

Work with module #4.

Fill in the data for XD 0W-30:

Temp 1 = 100
Vis 1 = 12.1
VI = 168
Temp of Interest = (Whatever temp in C you wish to view)

So you can build a chart to compare the viscosity of 2 or more oils at the colder temperatures.

A good method of learning how thick your favorite oil is at a variety of temperatures!

---

Thank you very much for the link, it sounds like an excellent resource for the into I need. Unfortunately I am getting a java brower error so the site doesn't work

 

[ringmaster]

quote:

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Originally posted by boxcartommie22:
both of those cst's are 30 wt. motul is a high 30wt...

---

The Motul in question is a 40wt so I am not sure what you are trying to say? I am leaning towards the XD-3 for cost reasons.

 

[bobo]

Following completion of my AutoRX rinse phase (1,350 miles) I will be switching to Esso XD3, 0w30, synthetic oil and plan on running it year round. I have a 1995 Nissan Maxima with 61,250 mostly highway miles on it. Going forward, I will likely continue to drive about 70% highway/30% city miles.

Will my fuel economy using XD3 likely be lower than running say Castrol GTX 5w30 dino oil? The winters on the Coast of BC are relatively mild and it never gets below -10C (+14F).

Thanks

 

[Blake Sobiloff]

quote:

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Originally posted by bobo:
Will my fuel economy using XD3 likely be lower than running say Castrol GTX 5w30 dino oil? The winters on the Coast of BC are relatively mild and it never gets below -10C (+14F).

---

Maybe slightly, but almost impossible to distinguish from normal variances in MPG due to traffic, weather, etc. It will depend on how long your trips are and how long you'd run the oil. The Esso won't shear down as quickly as the Castrol, so towards the end of an equivalent OCI the Castrol would be thinner, providing a minute improvement in MPG.

 

[greenjp]

It's just one measly unscientific data point

, but I think we saw reduced mileage with the 15W-50 that was in my Saab 9-5 Aero. I changed it out to 5W-40 a week or so ago, and the mileage on the computer immediately climbed up a couple mpgs, from ~25 to ~27.

jeff

 

[hominid7]

Not exactly on-topic, but I've attempted to track the gas mileage in my 2001 mazda 2.5 V6 using 5w-30 and 10w-30 to see if there is a measurable difference between the two. I've used dino in both grades and semi-synthetic in both grades (but never full synthetic).

I've noticed no real difference in the two. I did get one tank of 100% pure highway, no A/C, windows shut, running brand new semi-synthetic 5w-30 at 31MPG. That's higher than the car is rated at HWY, but i think it was just an unusual situation with a tail-wind, night highway driving at consistent 70 MPH with only 1 stop. I've never been able to duplicate it.

I've also experimented with gas and seems i get the best mileage with the mid-grade 89 octane than i do with either 87 or 91.

I've read through a great number of spec sheets and UOA's on various oils and more and more, especially with the newer SM formulations, the difference between 5w-30 and 10w-30 appears to be getting smaller and smaller. Many even share the same pour point. I think 10w-30's are blended on the thin side to allow them to meet the starburst requirements, and the 5w-30's are getting better at staying in grade and retaining more consistent film strength.

While i am in no way a synthetic enthusiast, i have been curious about the GC 0w-30 craze and have wanted to try a batch of it to see how my gas mileage does compared to 5w-30 and 10w-30. I suspect it will do no better. However my miles are not the easiest on a car. I drive approx 250 miles per week. At least 1/2 of that is short < 5 mile trips. On the weekends i make one or two 90 hwy mile roud-trips to Dallas and back. So i'm that helps to undo some of the damage done by the excessive short trips.

 

[AcuraSLX]

I tied 20-50 dino in my old 2.4L 90 Stanza. the economy went down only a little but engine cranked noticeably slower when starting. I think you would have to get a pretty big difference in viscosity to make a significant change in street driven fuel economy.

 

[ringmaster]

quote:

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Originally posted by AcuraSLX:
I tied 20-50 dino in my old 2.4L 90 Stanza. the economy went down only a little but engine cranked noticeably slower when starting. I think you would have to get a pretty big difference in viscosity to make a significant change in street driven fuel economy.

---

These are exactly my feelings but I wanted to bounce it past the experts on the site

before I dumped in the heavier stuff.

XD-3 here I come!

 

[bobo]

So, in fact the XD3 could provide higher MPG in the winter. In the summer, inflating the tires by an extra 2psi could well compensate for any shortfall in the XD3 fuel economy, which may be negligible at any rate.

 

[ecclestone]

Rergarding fuel economy V/s Viscosity, as a general rule within the oil industry that you gain 1% (read either performance or economy ) for every decrease in grading . ie going from a 30 to 20 to a SAE 10 .. The increase in performance translates to economy and may be used accordingly