28mpg->25mpg: castrol syntec 5w30 from 5w20 dyno

[rancur3p1c]

Feel free to skip down to the bold below if you want the tl;dr version.

I have a manual 06 Scion tc, engine year 08 and has 25k on the engine. Put 5w30 Castrol Syntec in it in the interest of better flow at 6kRPM to protect engine life when I floor it to redline from a stoplight

...my car is not "performance" but it's fast enough to make me happy

Anyways I used to get 28mpg on dyno 5w20 (Toyota spec) until about 3k when the VIIs wore out, when it would drop to about 25. When I put the Castrol Syntec in I was not expecting to drop to 25. I did this late fall last year right when it got cold and chalked it up to winter additives in the gas.

My question: I have a gallon of 5w30 Mobil1 full "synthetic". I'm wondering if I put it in, if the different Mobil1 formula might have better flow rate and give me the better gas mileage again. 3 miles*14gallons is 42 miles aka significantly further on a tank...kinda wish I had that back.

What is your recommendation?

 

[shrooms]

You might as well try the M1 and see what happens. It's very hard to tell what the results would be.

 

[bepperb]

Mail me the M1.

I still think there is another variable, but I guess if I were you I would run the M1 next and then go back to a 5-20. Or just stash the M1 for a later date, like when gas goes back down to 2 bucks a gallon. (happened last time).

 

[TFB1]

Originally Posted By: bepperb
Mail me the M1.

I still think there is another variable,


Agreed, I can't see loosing 3mpg even if it was filled with 20W-50...

 

[d00df00d]

to BITOG!

Originally Posted By: rancur3p1c
I have a manual 06 Scion tc, engine year 08 and has 25k on the engine. Put 5w30 Castrol Syntec in it in the interest of better flow at 6kRPM to protect engine life when I floor it to redline from a stoplight

...my car is not "performance" but it's fast enough to make me happy

5w30 won't give you "better flow at 6k RPM." It's a heavier viscosity that won't thin out as much when it gets hot, and will produce a slightly thicker film in your bearings. If anything, it will flow more slowly (although oil pressure will be higher -- that's different). All-in-all, it may or may not be what you want in your engine, depending on how it's designed and how hot your oil gets.

Either way, a decent 5w30 most likely won't hurt, but you are probably fine with a good 5w-20.


Originally Posted By: rancur3p1c
Anyways I used to get 28mpg on dyno 5w20 (Toyota spec) until about 3k when the VIIs wore out, when it would drop to about 25.

Quick note: I don't think VII shearing would produce this effect. If your MPG really did drop, it was most likely because of something else.


Originally Posted By: rancur3p1c
When I put the Castrol Syntec in I was not expecting to drop to 25. I did this late fall last year right when it got cold and chalked it up to winter additives in the gas.

Well, you pretty much said it: you can't really tell what produced the drop in MPG. I wouldn't blame the oil just yet.


On MPG changes in general: this has been covered several times, but the important part is that while it's easy to calculate MPG, it's really, really hard to figure out whether an increase or decrease is due to chance. You need several measurements under absolutely identical conditions that you have gone to great lengths to control, and then you need to use some statistical math to figure out whether the results are due to chance. Unless you see a swing of like 30%, I wouldn't put too much stock in it.


Originally Posted By: rancur3p1c
My question: I have a gallon of 5w30 Mobil1 full "synthetic". I'm wondering if I put it in, if the different Mobil1 formula might have better flow rate and give me the better gas mileage again. 3 miles*14gallons is 42 miles aka significantly further on a tank...kinda wish I had that back.

No way to tell in advance. Because you don't know if the MPG drop was real, let alone if it was because of the oil, you don't even know what you stand to gain by switching oils again.


Originally Posted By: rancur3p1c
What is your recommendation?

I would stick to 5w-20 or 0w-20 and just get the best one I could find. Mobil 1 or Castrol Edge would be my off-the-shelf picks. Toyota and Honda have 0w-20s that look good, too. RLI or Fuchs would be my picks if online ordering is an option.

 

[sicko]

You've already got the M1 so go ahead and try it.

Stick with an oil for a couple of oil changes, if you're not happy switch to another oil for a couple OCIs and see if you're happier with it. Repeat until you find the oil you're happy with

If you really want 5w30, but want it on the thinner side, check out Chevron Supreme or Havoline (same oil), they start out on the thinner side of oils and tend to shear less over the OCI.

Or maybe try a different brand 5w-20 than you were previously using. Check out Motorcraft 5w-20, it's a solid semi-synthetic oil at price that usually compares with conventional oils.

But I don't think your oil is causing the MPG drop if it's happening in the middle of an OCI

 

[dan3952]

I don't think you will be disappointed with the gas mileage of Mobil 1 5W20. The best gas mileage I ever got was 35 mpg on the highway and that was a 2.3 L engine with the 5W30 grade which is what it was rated for in the 1998 model year. I only give 1 to 1.5 mpg difference to any change in motor oil. I noticed slightly better gas mileage with my most recent fill where I had Rotella T in there before (the thickest choice of its grade). More ethanol in the fuel will give you less gas mileage. I can't be entirely sure if my latest tank is a summer fuel blend that is giving me better gas mileage than the winter blend

 

[rancur3p1c]

Originally Posted By: d00df00d
Well, you pretty much said it: you can't really tell what produced the drop in MPG. I wouldn't blame the oil just yet.


No? It's getting up to 85 today here...

I'm only at 3600miles so I'll still have this oil in the summer if they haven't already switched to non-winter gas.

 

[gathermewool]

I can say with 100% certainty that the 3 mpg drop is not even mostly due to the oil. Bold claim, I know...

 

[Silver02ex]

I would use the M1 and not let it go to waste. If you are so concern about gas mileage. Here's a tip. Stop flooring it from a stop light a few time and you'll see an increase in gas mileage.

 

[rancur3p1c]

Originally Posted By: Silver02ex
I would use the M1 and not let it go to waste. If you are so concern about gas mileage. Here's a tip. Stop flooring it from a stop light a few time and you'll see an increase in gas mileage.


I almost never do!!! I just want the engine to last me forever.

At any rate these calculations are with highway miles.

 

[d00df00d]

There's more to the "no-WOT" rule than you might think. Most cars are designed to run a tad rich at WOT for safety. Rich running can cause fuel dilution (fuel getting into the oil), which can break the oil down prematurely (in addition to the obvious waste of fuel). If you want to accelerate hard, use 80% throttle. It'll give you virtually the same acceleration as WOT, but without as much rich running.

 

[Xstang]

I really don't think the oil is the culprit here, if at all.

This is what I'd do instead:

1. Change spark plugs.
2. Run a bottle of fuel injector cleaner.
3. Replace air filter and fuel filter, if possible

Fuel MPG drops are not usually affected by oil. Going to a 30 weight oil should be perfectly fine, especially with summer right around the corner. Besides, if you drive the way you do, the oil should probably thin out/shear down to a 20 grade rather quickly.

My '03 camry has the exact same 2.4 DOHC inline-4 as your scion, and my manual says to run a 5w30, so honestly I'd stick with that.

If you're wanting to save money,hold on to that bottle of M1 for the next oil change.

 

[whip]

If you're that concerned about economy, stop flooring it from the stop lights.

 

[moto94536]

are you suprise? I used castrol syntec on my 2006 toyota camry v6 for 2 years. Recently I switch to chevron supreme. I get better mileage with the chevron supreme. So no more castrol oil for me. I will only use chevron supreme, mobil dino..


http://www.fuelly.com/driver/hondavtec/camry

 

[rancur3p1c]

Originally Posted By: moto94536
are you suprise? I used castrol syntec on my 2006 toyota camry v6 for 2 years. Recently I switch to chevron supreme. I get better mileage with the chevron supreme. So no more castrol oil for me. I will only use chevron supreme, mobil dino..


http://www.fuelly.com/driver/hondavtec/camry


Yes I am suprise. thanks for the report. I am currently planning to use the mobil1 5w30.

I am almost certain the MPG drops are due to oil. Back when I was using Dyno oil 5w20, and I would drop to 25mpg at 3000 miles, if I changed it I would instantly get back to 28mpg. This happened on 3 changes. Then, when it was time to change this last time and I went to the Castrol Syntec 5w30, the MPG never went back up!!! So I am certain it is the oil, not gas, not filter, not anything else.

This last tank (with the AC on full blast for most of the tank, I got 23.5mpg (albiet harder driving). Yikes. Normally would drop to 25.5/26 on hard/normal driving with AC.

 

[Steve S]

Originally Posted By: Xstang
I really don't think the oil is the culprit here, if at all.

If you're wanting to save money,hold on to that bottle of M1 for the next oil change.
Well to be realistic this is BOB Is The Oil GUY and oil is the cause of everything . For example I have an engine miss would 5w-20 oil fix it? I read this article that said how good 5w-20 oil is!!!

 

[Steve S]

Originally Posted By: rancur3p1c
Feel free to skip down to the bold below if you want the tl;dr version.

I have a manual 06 Scion tc, engine year 08 and has 25k on the engine. Put 5w30 Castrol Syntec in it in the interest of better flow at 6kRPM to protect engine life when I floor it to redline from a stoplight

...my car is not "performance" but it's fast enough to make me happy

Anyways I used to get 28mpg on dyno 5w20 (Toyota spec) until about 3k when the VIIs wore out, when it would drop to about 25. When I put the Castrol Syntec in I was not expecting to drop to 25. I did this late fall last year right when it got cold and chalked it up to winter additives in the gas.

My question: I have a gallon of 5w30 Mobil1 full "synthetic". I'm wondering if I put it in, if the different Mobil1 formula might have better flow rate and give me the better gas mileage again. 3 miles*14gallons is 42 miles aka significantly further on a tank...kinda wish I had that back.

What is your recommendation?
What is this flow craap at 6,000 RPM supposed to mean?

 

[friendly_jacek]

Originally Posted By: rancur3p1c

Anyways I used to get 28mpg on dyno 5w20 (Toyota spec) until about 3k when the VIIs wore out, when it would drop to about 25.


I don't understand that. If VII wear, viscosity goes down and economy should go up. Why would it be the opposite? We are talking about more than 10% difference!

 

[rancur3p1c]

Originally Posted By: friendly_jacek
Originally Posted By: rancur3p1c

Anyways I used to get 28mpg on dyno 5w20 (Toyota spec) until about 3k when the VIIs wore out, when it would drop to about 25.


I don't understand that. If VII wear, viscosity goes down and economy should go up. Why would it be the opposite? We are talking about more than 10% difference!


Pressure can push through the oil with worn out VIIs and create friction, but can't with the new oil?

I wondered about why myself, and read lots on that calsci guy's website, he kept talking about the VIIs, so I figured that was what mattered.

What is it then, if not the VIIs? TBN? That's just the ability to counteract acidity. That shouldn't impact mileage....