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Gregte 07-15-2008 05:20 PM

Larger oil filter for better FE?
I looked on EcoModder for info on this subject but didn't find any. Anyway, since a cold motor may actually pass oil thru a by-pass valve until it is warm enough to pass through the filter media it occurred to me that using the largest oil filter that will fit your vehicle should benefit FE since it takes energy to push the oil through the filter media.

Can anyone give me an opinion or better yet, actual numbers on how much this might benefit FE?

Lighter weight oil is definitely better for FE but there is a limit to how light you can go.

Daox 07-15-2008 05:35 PM

I never heard of a thermostat setup on just a basic engine. I've heard of them with oil coolers.

Gregte 07-15-2008 07:21 PM

Well, what my question is, do you think a larger sized oil filter would be FE beneficial rather than a small sized oil filter? I am not thinking in terms of doing anything to heat the oil, just wondering about the FE advantage of a larger filter.

Some engines, such as my 4 cyl. GMC Sonoma, come with a very small oil filter. I just finished cutting the motor mount area as required to accommodate the longer filter. My initial reason was simply to provide more filter area for the collection of dirt, but then it occurred to me that a larger filter should also make it easier for the engine driven, power robbing, oil pump to push oil thru it.

ConnClark 07-15-2008 07:31 PM

I wouldn't think it would result in much of an improvement in fuel economy. Your oil pump still has to force the oil through the engine and that pressure is going to make the oil filter pressure drop pale in comparison. Also most engines have a bypass valve that allows the oil to bypass the filter once the pressure across the filter reaches a certain limit.

I would think that the better filtration would lead to reduced wear on the engine. This better protection would keep the engine running better for a longer time and that would in turn improve FE.

Gregte 07-15-2008 07:47 PM


Originally Posted by ConnClark (Post 44346)
...Also most engines have a bypass valve that allows the oil to bypass the filter once the pressure across the filter reaches a certain limit....

My guess would also be that the resistance of the filter element is rather puny compared to the total resistance of oil flow.

But, just the fact that there is a bypass, in case the filter is plugged, or I would also assume in case it's 'just too cold', shows that the filter can offer a real resistance to oil flow.

I notice that my oil pressure is always up around 80 psi when I start, regardless of RPM, and gradually reduces to 40 or so once it is fully warmed up (1/2 hr. driving time). But since it is at 80 psi no matter the RPM I have always assumed it is likely flowing the oil thru the bypass, at least when above idle speed. This is true even when using 0W-30 Mobil-1.

It must take some HP to push that oil but like you say, the filter itself is probably a very small amount of the total oil flow resistance.

dremd 07-15-2008 11:12 PM

AirCooled VW's had an oil cooler thermostat :-)

I don't have scientific data, but I would change my oil in the supra when the mpg dropped 2 tanks in a row from expected, then it would return. Could be psychological.
I'm running an oil guard on the Golf for just that reason.

justpassntime 07-16-2008 04:54 AM

The size of the filter is just that, the size of the filter. The filter media is the same for the particular oil filter type and brand and would have nothing to do with the pressure required for the flow of oil.

JohnnyGrey 07-16-2008 09:29 AM

I know that some Neon guys use Viper filters. If you change your oil every 3K, I don't see the benefit to going larger. However, if you're using extended-interval synthetics, a filter with a higher capacity could prove beneficial since the oil and filter would reach the end of their service lives at about the same time.

Shawn D. 07-16-2008 11:44 AM


Originally Posted by Daox (Post 44322)
I never heard of a thermostat setup on just a basic engine. I've heard of them with oil coolers.

He's not talking about a thermostat. Cold oil is more viscous, thus causing a higher pressure differential across the filter media. To ensure sufficient flow and prevent media damage/blowout, a spring-loaded bypass is provided so the oil can bypass the filter and continue on to the galleys.

wagonman76 07-16-2008 12:21 PM

A larger filter would have more square inches of filter media. So that means when the same amount of oil passes through the filter, the velocity through each pore is less because there are more available. So less pressure is needed to push cold oil through the filter and less use of the bypass valve. Also the filter will stay cleaner longer since there is more media to fill with the same amount of dirt.

Not sure how much of this actually comes into play with regular change intervals.

But I mainly just use bigger filters on my cars because they are a lot easier to get a hold of with the filter wrench. I use the longer 3980 rather than the shorter stock 3387A.

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