Oil viscosity/brand and MPG.....

[zoomzoom]

Good point.Right after I put GC in I bought new set of tires that are high perfomance and 10% wider then stock(225 vs 205). So one would expect that my fuel economy would go down and it has not, which leads me to think that GC has perfomed really well since despite wider and more agressive tires it returned same MPG as M1 from winter before.
I use chevron gas 95% of the time so that didn't change. Air filter is changed every 30K so I'm almost due for a change but after reading some discussions about air filters I think I could leave it in for 60K or even longer without any problems.

 

[haley10]

I disagree with a lot of the board members on the air filter issue. I prefer to keep one that is reasonably clean. It will affect your fuel economy.

I know about the dirty air filter giving better uoa's theory. I just don't subscribe to it.

No need to go overboard, but I wouldn't go too long. The seals will age and the element can deteriorate to a degree.

 

[jason07-1zzfe]

It's not a theory.

And unless you live in an incredibly dusty environment, even the mfr recommended change is very conservative.

Have 55k miles on original air filter and getting mpg as good as ever, actually got best highway mpg ever 2 weeks ago.

 

[sjlee]

I don't know if the oil has much to do with your fluctuations in gas mileage... at least not the sole/primary reason.

You will notice that the gas mileage is worse in the winter than in the summer, which I've noticed as well on my car (with the same oil and tires). Probably due to letting the car idle while it warms up, the engine not running as efficiently due to the colder temps, driving through snow vs. clean pavement, etc.

Even though your new tires are wider and high performance, you also have to consider the rolling resistance. Even though your tires are wider, they may have less rolling resistance than your previous tires (which were narrower).

In addition, you also have to take into consideration if you did more city vs. highway driving, if the gas you used at certain times was different... you get the picture.

If you want to really see if there's any difference, try using the same oil all year round (all four seasons), then checking your gas mileage.

 

[sjlee]

quote:

---

Originally posted by Jason Troxell:
It's not a theory.

And unless you live in an incredibly dusty environment, even the mfr recommended change is very conservative.

Have 55k miles on original air filter and getting mpg as good as ever, actually got best highway mpg ever 2 weeks ago.

---

Is that 55k miles without even cleaning it (i.e. using an air hose to blow the dirt off)?

That seems like a really long time to leave an air filter in the car. I think my owner's manual recommends changing it every 12k.

 

[jason07-1zzfe]

quote:

---

Originally posted by sjlee:
Is that 55k miles without even cleaning it (i.e. using an air hose to blow the dirt off)?

---

Yup

 

[haley10]

Originally posted by Jason Troxell:
[QB] even the mfr recommended change is very conservative.

Well, I'm glad to see they are conservative about something. 10K on SL dino oil, et., etc.

I'm sure it depends on filter quality and driving conditions.

Doesn't work here. I guess where you live colors the judgement.

 

[Robbie Alexander]

IMO based on my experiences... you can run with an air filter up to the point milage suffers.
If you know from experience of your application;
you may be able to go 15K or 20K or 30K... every car and application will be different.
For me in the Houston market every 15-20K is about right. I can push it to the 25K level but for my application that is too far.
I buy filters when they go on sale and pick up 10-12 at a clip. I'm down to about 8 in stock.

As far as keeping them real clean, I have not seen with my setup any reason to keep them overly clean, just within reason.

quote:

---

Originally posted by haley10:
I disagree with a lot of the board members on the air filter issue. I prefer to keep one that is reasonably clean. It will affect your fuel economy.*-*

---

 

[Robbie Alexander]

Can have, depending on maintenance and application.
Besides proper inflation, and I'm no mechanic, but I believe keeping the fuel filter within it's proper schedule is very important.
I don't care what any mechanics tell me about not needing to change it so often, but I find not only the truck runs better but MPG remains higher when I change for my application around 30-40K, I do go longer sometimes but IMO for my application this is a good time to change on my Tacoma.

quote:

---

Originally posted by sjlee:
I don't know if the oil has much to do with your fluctuations in gas mileage... at least not the sole/primary reason.
-*-*

---

 

[zoomzoom]

I keep track of my MPG since I bought the 2000 Mazda 626 V6 5sp and here are some numbers I got using different oils and viscosities. Interesting to note that my MPG improved using higher viscosity oil M1 0W-40 which is in the car now???
Maybe Auto-RX had something to do with this?

OCI**Miles**Oil**MPG**Season
4K**0-36000**Castrol Dino**25.7**first 2 years
10K**36000-46000**M1 10W-30**27.1**summer
9K**46000-55000**M1 5W-30**26.0**winter
9K**55000-64000**M1 10W-30**27.0**summer
9K**64000-73000**GC 0W-30**26.0**winter
5K**73000-78000**M1 0W-20**25.8**spring
3K**78000-81000**Auto RX/castrol/rotella**27.1**spring
?K**81000-?????**M1 0W-40**27.4**summer

 

[haley10]

Different tires and air filter changes might account for these variations also, as well as different fuel.

Too close to call.

 

[oilyriser]

I have some more data to add:

62 mph, highway driving, compared to 10w30:
Subaru Legacy: 15w40 used about 2.5% more fuel
Mazda 929 V6: 20w50-- 26 mpg vs. 30 mpg

In both cases, I could feel the extra drag on the engine.

At high loads, the viscous drag of the oil will be much smaller in comparison to the total load, so the effect of oil type will be much less noticeable.

 

[springnr]

Chart trend looks to be showing summer time verses winter time gas formula changes.

[ July 17, 2004, 05:39 AM: Message edited by: springnr ]