Engine oil weight and fuel economy

[Flatland2D]

I currently have Mobil 1 15w-50 in my engine. I did this in attempt to stop a smoking problem I had only at high rpms (started around 6k). Previously I had 5w-30 which was the recommended oil, but down here in Texas it gets really hot so I went up. I'm thinking about compromising with 10w-30. Anyone think I'll gain another mpg or two by using a thinner oil? I'll do at least one more tire pressure test to verify my results, but then it might be interesting to change my oil and see what happens.

[SVOboy]

I think that you can gain 1 mpg through switching your oil. I asked if I could run 5w 20 in my car a while back but I was told no by the honda people, so I am sticking with my 5w 30, but you're using really heavy oil now, I think you can go to 10w 30 without a problem if you can't use 5w 30.

[dfoxengr]

i use 5/30 in the motor, and 10/30 in the tranny for hondas...

you could use a lighter one, as long as weather permits it.

[SVOboy]

What kinda temps would I have to be in the use a 5w20?

[dfoxengr]

just warmer climate im pretty sure.

[chasgood]

5w20 is something Ford came up with. It is a synthetic blend.
I hear the best oil to save gas with is Mobil 1 synthetic 0w30.
As well as giving a bit better mileage you can go farther between changes. I use Mobil 1 5w30 and change it every 6000mi or 6months. If I had a non turbo car I would even go farther between changes.

[SVOboy]

I got 5k miles, what do you think about 0x30 in a car recommended for 5w30?

[dfoxengr]

Originally Posted by dfoxengr

as long as weather permits it.

[MetroMPG]

Originally Posted by SVOboy

I got 5k miles, what do you think about 0x30 in a car recommended for 5w30?

did you end up switching? or staying.

i'm also wondering about 0w30. how would you know if you were using too light weight? or would you just have to find out when your engine is worn out early?

[SVOboy]

Think you'd just have to find out and live with it, there might be a method to diagnose oil, but I do not know it. I ended up staying because I couldn't find 0w30 locally and the car was long overdue for a change. Got another change coming up in 2k miles and I'm waiting on results from h-t where a guy is dyno testing like 20 kinds of oil. (I'll try to pick my brand by this, but I'll want 0w30.)

[rh77]

I used to run Mobil 1 0W30 in my '99 Civic Si, although it required 5W30-dino (for wear and economy since I ran it pretty hard). I was told that the synthetic equivalent of Zero-Weight synthetic is similar to 5-weight petroleum-based. I had to be careful with it -- since it was so light, I lost a lot between changes -- so much in fact, the ECU shut-down the VTEC system on me during an autocross cornering maneuver (since it's oil-pressure based). The rev-limiter cut way early -- I thought I broke something, took it to the dealer closeby, added some oil, reset the code, and I kept a better eye on things. After 2000 miles, you don't think to check the dipstick, but I should have.

Basically, check your oil level often if you to 0W.

RH77

[MetroMPG]

oil consumption has a lot to do with how hard you drive, is what you're saying, right?

i used to run 5/30 syn in my 89 accord with almost 400,000 kms on it, and it didn't use oil between changes. but i drove it very relaxed (55-60 mph hwy).

a couple of years ago i went across the country in it at slightly higher than normal speeds (65-70) and noticed it used a little bit of oil in 5000 kms (half a liter).

[SVOboy]

I'm also tempted by 5w20 and 0w20, though I think they stopped making the green 0w20 like a year ago. I've just learned newer honda d17 engines run on 5w20 from the factory.

[MetroMPG]

the insight runs 0w20

http://www.insightcentral.net/demo/about-engine.html

[MetroMPG]

don't know if this is true, but it might be an option for those concerned about going all out to 0w20.

you could do a 5w30 - 0w20 mix.

mixing different weight oil does nothing more than give you a hybrid weight. nothing to worry about. (source)

or...

years ago I asked an oil expert on the Compuserve CARS forum if there was a downside in mixing different weights of Mobil 1 to arrive at something approaching a 15W40. He stated my mix would be close to this weight in characteristics. So that is what I do. (source)

...although i've selected supporting claims. if you do a google search, you will find opinions on both sides of the fence. facts on the other hand (or official information) are harder to find.

that said, i've always read that synthetics are fully compatible with other synthetics and mineral based oils. with a broad claim like that, it seems logical that you can mix weights also.

MIXING AMSOIL
AMSOIL ASL is compatible with conventional and synthetic motor oils. Mixing AMSOIL motor oils with other oils, however, will shorten the oil life expectancy and reduce the performance benefits. (source)

the last sentence makes sense, if you're mixing syn with mineral.

we've all probably mixed syn & mineral of differing weights at some point. i have, in all the vehicles i've owned - usually because i'm short a liter or maybe half at oil change time, or topping up between oil changes with something else.

i'll probably try a 0w20 mix at my next change (spring, unfortunately - this would really help now).

[SVOboy]

So you'll be mixing for a 2.5w25? Sounds pretty interesting indeed. I wonder now about new versus old oil for gas mileage.

[Compaq888]

Since the oil is thinner would the engine rev better???
Right now I'm using Royal purple 10W-30. I have never got such high mpg with regular oil or Mobil 1.

[chesspirate]

Lets all get this straight. 0w30 protects at the same temp as 5w30 and 10w30, the first number just says how the oil performs in cold temps while the second number is the protection number tested at certain operating temps. Similar theory to what Metro said in the synthetic oil thread about only really helping in the cold. Sooooo, in colder areas a lighter first number could help, where in warmer climates in summer time, as long as the second number stays constant it shouldn't make any difference whatsoever. And weight is weight the numbers mean the same thing for synthetics as they do dino's the only possible explanation could be the guy knew the exact weight (legally oils fall in to a range so a 5w30 could actually be a 5.5w32 for instance, i'm not sure on what the range is off the top of my head.) Google Bob is the oil guy and start reading.

[MetroMPG]

nut job that i am, i went ahead and swapped out 1L of 5w30 syn for 1L of 0w20 syn from my car...

mixing different weight oil... gives you a hybrid weight. nothing to worry about.

so i am now running 3.3w26.7

i just went crazy. also i burned my thumb on the drain plug.

[SVOboy]

Haha. I'm putting some 5w20 in my friend's civic this weekend because I saw it for sale and figured WTF. I had something important to tell you metro, but now I forget, and now I remembered again. You're site is number one when you search "block heater mpg" on goodle.

[MetroMPG]

i'm not surprised about the google position - the whole reason i put that page together is because i couldn't find any block heater comparisons anywhere on the web. so now everyone is finding it. that page, and my page about winter mpg losses, are the 2 most search-engined pages on my site.

[jamescartagena]

I found this article on the SmartGas website by Louis LaPointe dated April 2005. I put in excerpts here but basically he found his mileage increased when he put a heavier weight oil in his vehicles. Anyone willing to try this? I'll try it in spring when I am due for my oil change.

While playing the Mileage Game all that time, we investigated many different oils, special fuel additives, floatless carburetors, special ignitions and various other techniques to improve mileage. To hell with horsepower. I was only interested in MPG. Very few things really did as people claimed or performed according to rumor. It proved tough to squeeze more MPG from a gallon of gasoline or diesel fuel. Many combinations dropped MPG. While horsepower was easy to come by, MPG was really difficult. Dozens of items could be bought to increase power in any car. But that was too easy. Better mileage was tough, except that nobody cared because gas was so cheap back them. People thought I was silly for doing what I did by continually testing fuels and oils. For instance in Alabama I once lost a camshaft in my 1949 Olds due to using a purple 10W-30 oil. An engine builder suggested I switch to straight 40-weight truck oil to prevent another flat cam. The McGurk camshaft worked just fine after that. But my mileage went up in that car after the switch to the thicker oil. That went against everything I believed at the time, so I studied the science of lubrication or Tribology as a result. In 1967, I found a job testing lubricants and soon learned the real facts about oils, not by rumor or hearsay but by actual testing and analysis. Today we make oil testers for which I own a patent. But hardly anyone cares to view the truth about oils. They prefer to believe ads that appear like mindless propaganda, offering zero data. They are the slaves of advertising.

We just purchased a 1995 Mazda stick-shift 2.3-liter pickup to complement the Neon for testing. We first found a baseline in its as-purchased shape of 13.4 MPG in the city. Then we used Torco motorcycle T-4M 20W-50 engine oil, Baldwin filters, acetone with additives listed below, a new FOG device, NGK V-power plugs, Torco 75W-140 gear lube and other changes like we do with all the cars we use for mileage testing. We expected to double the mileage figures--as we have with many other vehicles. On a first test drive up North on Shell gas, the MPG was just short of 24. Then we added a couple of quarts of 40-weight oil and a new Baldwin oil filter along with 6 ounces of acetone into a full tank of gasoline. What a difference that made. There is noticeably better pickup and smoother idling. The idle speed went up from 800 to 900 RPM. The acceleration above 60 MPH was quite poor at first, even at full throttle. But after just these three little changes, the Mazda pickup seems to have better pickup. The exhaust pipe used to be sooty and black. The exhaust pipe after a couple of days became brown and now is so clean, my finger does not pick up anything. I attribute that to the acetone mix.

[JanGeo]

You guys ever hear of an oil pressure gauge??

If the oil is too thin at any temperature then the oil pressure will drop. IF it is too thick then the bypass in the pump will kick in and you waste power pumping oil back into the oil pan instead of through the filter and engine. All you need to do is get an oil pressure gauge connected and you can tell when the oil is too thin or dead worn out by the pressure drop. The best test for worn out oil is between your fingers - if it is slippery it is still good.

As far as additives I have used teflon additives from Slick50 and ProMotion in all my cars after they are broken in properly and beat on them and abuse the oil (castrol regular and more recently syntec blend) and have not had any engine failures. I also put the slick50 gear lube in the tranny and that although takes a while to start working helps also. Any additive that requires constantly adding for each oil change is not what you want to be using as it ends up costing too much usually.

[jamescartagena]

Check the following website out I believe it is www.synlube.com. Although the sell their own "special oil" and have to push it on the website, they do have interesting reading on mineral and synthetic oils. Very detailed information on the different types of synthetics. Anyway very good reading.

[MetroMPG]

Originally Posted by JanGeo

You guys ever hear of an oil pressure gauge??

you know, i've never owned or even driven a car with an oil pressure gauge... no, i think maybe there was one in a vw cabrio i fixed up. but i guess i didn't look at it too much. i suppose that's why it never occurred to me it would tell me if my oil was too thin. i knew there must be a simple answer.

now a bunch of questions...

do you know if a gauge can be easily retrofitted? or can you just hook up something temporarily? would the gauge just go in the spot the existing pressure sending unit is (i think that's what it's called)? i assume the existing unit is just a binary device with a threshold for the idiot light.

i'm just being lazy, i'm sure i could look up this info on the web.

[SVOboy]

do you know if a gauge can be easily retrofitted? or can you just hook up something temporarily?

Yes yes. Auto stores sell crappy oil pressure gauges for 15 bucks in my neck of the woods, you just hook it up and you can take it right off if you want.

[JanGeo]

Yup the sending unit is a on off switch and get this - it turns on below 6-7 psi so by the time that idiot light comes on - you have probably cooked the motor! I don't know if the computer monitors it or not but it turns on at low pressure and is open at high pressure so if you disconnect it you should be ok. A oil pressure gauge can be mechanical with a small hose into the cockpit which sometimes takes a while to respond to pressure changes if the line is long and small in diameter restricting oil flow or electric with a variable sending unit which can fail and respond faster but not leak into the dashboard. The hole should be a standard pipe thread hole.

[krousdb]

Originally Posted by MetroMPG

nut job that i am, i went ahead and swapped out 1L of 5w30 syn for 1L of 0w20 syn from my car.

I have run 0W-20 Mobil 1 on the Prius for 62k miles, changing every 12 - 15k miles. No problems so far.

I have the same 0W-20 in the del Sol, both engine and tranny.
So far, so good.

Dan

[SVOboy]

I have run 0W-20 Mobil 1 on the Prius for 62k miles, changing every 12 - 15k miles. No problems so far.

I have the same 0W-20 in the del Sol, both engine and tranny.
So far, so good.

Dan

Can I buy it at autozone? I will do the same thing in a few miles time.

What filters do you use?

[MetroMPG]

Originally Posted by krousdb

I have run 0W-20 Mobil 1 on the Prius for 62k miles, changing every 12 - 15k miles. No problems so far.

my main reluctance to going to full 0w20 in my car is my belief that its suzuki motor isn't as well engineered or built as the honda/toyota units. i probably don't benefit from the same tolerances that permit you to use it safely in those engines.

however, this is conjecture on my part. unless i try an oil pressure gauge, i won't know for sure.