Larger oil filter for better FE?

[Goldenfrog]

I use a regular filter but I change it, and top off the oil, at about 1000 miles. It just makes sense to me to keep a clean filter on it. I just grab a Fram at Wallyworld for like $4. My filter is right on the front of the engine. So no sweat involved. I change the oil completely when it looks and FEELS dirty, which is a long time with all the clean filters going on.

I have only put ~12,500 on my car since Sept 04 and 2,500 of that was driving it from where I bought/rebuilt it.

[cfg83]

Hello -

Don't know if this will help, but I read about one dude who claimed he got more HP on his racer when his oil level was lower. Based on that lesson, he lowered the oil level on his Saturn by increasing his filter size. Because the filter is bigger, the dipstick reads 1/2 pint less.

CarloSW2

[trask768]

I own a small industrial filter company, and I just switched all the oil filters in my small fleet of company cars over to a longer oil filter. I drive a Toyota Echo and didn't have to make any modifications to the car to make the change. Since I work in the filtration industry, I thought I'd share my reasons for doing so, as well as some of the technical aspects of switching to a longer oil filter for any that are interested.

First off, I recommend checking the specs of your new filter with the filter manufacturer's tech department before making the change, as you can damage your car if you accidentally put a filter on there with a higher bypass setting or micron rating than what the OEM recommends. Also, it's possible you will void your car's warranty by using a filter that's not recommended by the factory. I suggest sticking with a high quality filter OEM such as Baldwin, Mann, or Donaldson. I'd probably avoid Napa or Wix.

My second recommendation is to fill your longer oil filter half-way up with oil before installing it. If you can't do this, you may want to stick with the original filter. Otherwise, you car will run "dry" on startup (very little oil in it) a little longer than usual. This could damage your engine.

I changed from a Baldwin B33 oil filter to a Baldwin B7238. I double-checked with the factory and compared the surface area of the two filters (this is probably the most important spec), as well as making sure that the internal bypass valve and micron rating were the same between the two filters. Basically, the two filters were the same, except one filter had 88.6 square inches (B33) of media, and the other had 163.8 square inches (B7238).

The reason that surface plays such a big role is because it lowers the pressure drop across the filter. And yes, this pressure drop can be substantial (I think up to 20 psi when dirty - same as the bypass valve setting). Not only does this reduce the amount of work needed to pump oil through the filter, it also allows the filter to remove particulate more efficiently and operate effectively for a longer period of time. In fact, the biggest reason I changed to an longer oil filter wasn't to improve MPG, but to improve vehicle performance during extended oil-drain intervals. In other words, if someone went 2500 miles past the usual oil-change point, the filter would still perform well.

However, I have noticed a very, very slight increase in fuel efficiency, although I have not measured the difference scientifically. I've purchased a ScanGauge II from amazon and plan to try and test the difference the next time I change oil. I doubt if it's a huge difference at first, but might become more noticeable the closer the car is to an oil change.

In the long term, it will definitely improve the cleanliness of your engine and keep your car running longer. That in itself is probably justification for the mod.

Also, this can be a relatively inexpensive mod. In my case, the longer filter only took the investment in time to make sure everything was kosher, plus an extra buck or two for each filter.

Hope this is helpful.

[cfg83]

trask768 -

Welcome to EM and thanks for the feedback! I like the "safety first" information. I didn't know about half-filling the filter with oil during installation.

CarloSW2

[getnpsi]

Having oil analysed and safely being able to go another 1000-2000-3000 miles leads to less oil purchases at the store, leaving decent money saved with no mpg change. I use 5.0 mustang filters on my toyotas, and on my neon. This aspire is a tough one to use a larger filter (honda's thread) and it's just a few ounces difference.

[Goldenfrog]

One of the first things my dad taught me about cars was to fill the new oil filter before installing it. Also to but a little clean oil on the rubber seal for a good seat.

[dann_04]

I've always heard a larger filter drops your oil pressure once warmed up, also that it takes more oil to fill to capacity, becasue of larger size in which case the engine has to move more oil through the engine, which can then cause more work for the pump(which would cause worse mpg's) or heat problems(like in old vw's where if you put a deeper sump without a deeper pick up the cold oil would sink to the bottom and the hot oil would float on top of the cold and be picked up again and recirculated till the engine overheated.) There's more oil to cool, will that small amount make a difference? I don't know but those are the theories i've heard. Don't flame me just putting in what i've heard. Also there would be more oil to warm, so wouldn't it take a little longer to heat up thus also causing lower mpg's?

[metromizer]

Originally Posted by trask768

I own a small industrial filter company, and I just switched all the oil filters in my small fleet of company cars over to a longer oil filter.

The reason that surface plays such a big role is because it lowers the pressure drop across the filter. And yes, this pressure drop can be substantial (I think up to 20 psi when dirty - same as the bypass valve setting). Not only does this reduce the amount of work needed to pump oil through the filter

VERY helpful, great information. I have a question about your conclusion regarding losses associated with a relatively more restrictive filter:

If my bypass valve pops at 20psi, and while running at hiway speeds my engine sees about 40psi, then my oil bypassing the filter most of the time, right? At idle, my oil pressure might be 15psi, bypass valve closed, thus only filtering my oil while I am at a stop light, right? If that's right, then the only time I could possibly be using less power to turn my oil pump is when the pump is putting out less than 20psi, so I only save fuel under low loading situations, do I have that right?

With more filtering area you should be able to go more miles between filter changes if you wanted to, and reduce your chances of a clogged filter like you say. The old O-Berg aftermarket filters used to have a pressure sensor option, 'tattle-tale' they called it, to notify the driver of a greater than 15psi pressure differential across the filter: If the car builder wired it up right, when the separate filter idiot light comes on, it's time to clean the filter. Those were ok filters, just not enough square inches. Most racers I know have gotten away from that and gone to a System 1 or similar pleated stainless steel screen type filter. With or without bypass is still debated.

[trask768]

I've always heard a larger filter drops your oil pressure once warmed up

A bigger oil filter is not going to cause an oil pressure drop. In fact, it should help an aging oil pump perform better, as it is easier to pump the oil through the filter.

it takes more oil to fill to capacity

A bigger oil filter will slightly increase how much oil it takes to reach capacity - however it's very small difference (in my case about 1/2 cup) and easy to either compensate for the difference by adding extra oil or, in my case, ignore entirely since my oil level indicator still showed full.

in which case the engine has to move more oil through the engine, which can then cause more work for the pump

You aren't moving any additional oil through the engine. Your oil filter should have an anti-drainback valve to prevent oil from escaping the filter when the engine is off. Your pump will have less work to do since it will be easier to push the oil through the filter due to the greater surface area of the filter.

or heat problems

You aren't exposing the oil to any additional sources of heat, so the larger oil filter will not cause any heat problems.

If my bypass valve pops at 20psi, and while running at hiway speeds my engine sees about 40psi, then my oil bypassing the filter most of the time, right?

That's a common misconception about bypass valves, although your conclusion isn't necessarily incorrect. They don't operate on system pressure, they operate on differential pressure, which is the difference in pressure between the inlet of the oil filter and the outlet of the oil filter. Under certain conditions, a very dirty OEM filter may have a 20 psi pressure drop. Under the same conditions, a longer filter (with double the surface area) would probably have around a 8 psi pressure drop. Pressure drop across a filter is directly affected by several variables - as you increase these things, you'll increase the pressure drop across the filter: viscosity of the oil, flow rate of oil through filter, time in service of oil filter. However, there's an inverse relationship between the pressure drop across the filter and the surface area of the filter. In other words, as you increase the surface area of the filter, you'll decrease the pressure drop. In addition, an increase in oil filter surface area will actually decrease the effect that higher oil visocities, higher flow rates, and longer time in service will have on the pressure drop.

With or without bypass is still debated.

You definitely want a bypass on your oil filter, especially for racing. Without a bypass, as it gets dirtier, an oil filter will restrict flow more and more (and decrease oil pressure more and more) until eventually, your engine is so starved for oil that it locks up.

[vtec-e]

I've read about them. Good stuff i reckon, if not a little strange to be filtering with toilet paper!

ollie