Oil filters... more than you EVER wanted to know
An oil filter is an oil filter, right?
Well yes. And a horse is a horse, of course, of course.
But for ages, I've been told to steer clear of Fram filters. "Avoid the orange can, " they repeat as a chorus.
But why?
Well, I thought I'd have a little fun, and see what the difference is. So I rolled up to Cambodian Tire to buy a Fram "Weatherguard" CPH3569 ($6.11) and a Bosch 72174 ($5.89) to compare. Both are standard issue for a VW 1.6 or 1.9 diesel.
Then, I cut the tops so I could pull them apart and see what's what:
Excited yet?!? Oh boy!
Right off the bat, there are some apparent differences. First off, the filter paper is glued to cardboard ends on the Fram, metal on the Bosch. Without even measuring, the Bosch filter obviously has FAR more pleats and therefore, more filter medium.
Those flat steel springs are what keep the filters pressed against the filter heads. On the Fram one, the red dot is the pressure relief bypass. In the Bosch filter, that's integrated into the bottom metal end. More about that later.
Now, I know youze are all excited about filter mediums and bypasses, but lets stop and look at a detail first. Lets look at how the filters seal up to the tops of the filter "head".
On the Bosch, the filter paper is capped at both ends in metal, so a rubber gasket fits between the filter top and the head. That gasket serves two purposes. First, it seals between the two parts, but its wide shoulder also to serves as a "drainback" valve, not allowing oil to syphon out of the filter when the engine is turned off. Anyway, it's a pretty simple design and it seals up nicely:
On the Fram, you can see the black rubber "drainback" ring, with the little blue mark on it. On mine, it sealed well the whole way around. I've seen pictures of ones where it doesn't, which would defeat the whole purpose. But they got this one on right. Congrats! The filter head seals against the filter end without a gasket, probably with the assumption that the cardboard end serves as a "good enough" gasket:
OK, now onto the fun stuff. Take the best breadknife in the house, and cut the filter paper off the bases. I actually had to use a hacksaw on the Bosch, because the perforated column in the middle is tack welded to the ends, so you have to saw through it. The Fram was way easier, as soon as you got one end cut, the perforated column just falls out. It's also worth noting that the cardboard ends were really flimsy, and got beat in the process.
All in all, the Fram was hard to take apart with having it FALL apart. The Bosh was just harder to take apart.
Now back to those pressure relief bypasses I mentioned earlier... whazzatfore, you ask? Well, if you are like my mom and change your filter every 2-3 years, it's going to get plugged up with old scuzzie oil and shattered dreams. As an analogy, imagine a vacuum filter that plugs up. After a while, nothing will flow through and you have to change it. Well, you can't have an oil filter just plug up, because if oil stopped passing through, your engine would seize and your whole morning would be ruined.
The Bosch bypass can only be seen by taking the filter apart. It's spot welded to the inside of the filter base, and has a tight little spring that pushes down on thick little disk. When there is enough pressure on the back of the base, the spring is compressed and oil gets passed:
The Fram one is incorporated into the flat steel spring that the filter sits on in the "can". The reddish wire spring keeps tension on the red plastic plug. When pressure gets high enough, the bypass opens. Notable on this one is the fact that one of the shoulders of the red plastic plug was not properly fitted over the spring. Nice.
For my next trick, I stretched out the paper filter to compare it side to side. Some poor planning on my part is evident here. Ideally, I should have stretched it out on the floor and taken a picture. Problem is it was mid-day and our floors REALLY needed to be vacuumed, what with having 3 dogs laying around. So I pinned them and stretched them out on the cupboard door instead. Glad I did too, because it shows what a fine finish you can get if you use good paint, a good brush and a delicate stroke. Some people ask if those cupboards were sprayed, but if you look carefully you will see very fine brush marks. I'm really proud of those cupboard doors.
Anyway, problem was that they weren't quite tall enough for a side by side comparison of filter paper. Here's the scoop... the Fram is the ONE piece on the left: 150 cms long. The two pieces on the right are the Bosch; 150 cm & 90 cm for a total of 240 cm.
So, taking into account the overall width of the paper, 9.5 cms for both, I end up with a dramatic difference in surface area:
Fram: 1425 cm2
Bosch: 2280 cm2... 60% more surface area!
Another thing that's noteworthy: When I was stretching the filters out, I had to be careful to not tear the Fram. Even being gentle, it started to tear at the pleats in several places:
So there you have it. The Fram filter is probably just fine, so long as it doesn't plug up 40% earlier, the paper isn't torn, and the bypass spring and plug aren't messed up.
Further discussion on the PelicanParts forum
Well yes. And a horse is a horse, of course, of course.
But for ages, I've been told to steer clear of Fram filters. "Avoid the orange can, " they repeat as a chorus.
But why?
Well, I thought I'd have a little fun, and see what the difference is. So I rolled up to Cambodian Tire to buy a Fram "Weatherguard" CPH3569 ($6.11) and a Bosch 72174 ($5.89) to compare. Both are standard issue for a VW 1.6 or 1.9 diesel.
Then, I cut the tops so I could pull them apart and see what's what:
Excited yet?!? Oh boy!
Right off the bat, there are some apparent differences. First off, the filter paper is glued to cardboard ends on the Fram, metal on the Bosch. Without even measuring, the Bosch filter obviously has FAR more pleats and therefore, more filter medium.
Those flat steel springs are what keep the filters pressed against the filter heads. On the Fram one, the red dot is the pressure relief bypass. In the Bosch filter, that's integrated into the bottom metal end. More about that later.
Now, I know youze are all excited about filter mediums and bypasses, but lets stop and look at a detail first. Lets look at how the filters seal up to the tops of the filter "head".
On the Bosch, the filter paper is capped at both ends in metal, so a rubber gasket fits between the filter top and the head. That gasket serves two purposes. First, it seals between the two parts, but its wide shoulder also to serves as a "drainback" valve, not allowing oil to syphon out of the filter when the engine is turned off. Anyway, it's a pretty simple design and it seals up nicely:
On the Fram, you can see the black rubber "drainback" ring, with the little blue mark on it. On mine, it sealed well the whole way around. I've seen pictures of ones where it doesn't, which would defeat the whole purpose. But they got this one on right. Congrats! The filter head seals against the filter end without a gasket, probably with the assumption that the cardboard end serves as a "good enough" gasket:
OK, now onto the fun stuff. Take the best breadknife in the house, and cut the filter paper off the bases. I actually had to use a hacksaw on the Bosch, because the perforated column in the middle is tack welded to the ends, so you have to saw through it. The Fram was way easier, as soon as you got one end cut, the perforated column just falls out. It's also worth noting that the cardboard ends were really flimsy, and got beat in the process.
All in all, the Fram was hard to take apart with having it FALL apart. The Bosh was just harder to take apart.
Now back to those pressure relief bypasses I mentioned earlier... whazzatfore, you ask? Well, if you are like my mom and change your filter every 2-3 years, it's going to get plugged up with old scuzzie oil and shattered dreams. As an analogy, imagine a vacuum filter that plugs up. After a while, nothing will flow through and you have to change it. Well, you can't have an oil filter just plug up, because if oil stopped passing through, your engine would seize and your whole morning would be ruined.
The Bosch bypass can only be seen by taking the filter apart. It's spot welded to the inside of the filter base, and has a tight little spring that pushes down on thick little disk. When there is enough pressure on the back of the base, the spring is compressed and oil gets passed:
The Fram one is incorporated into the flat steel spring that the filter sits on in the "can". The reddish wire spring keeps tension on the red plastic plug. When pressure gets high enough, the bypass opens. Notable on this one is the fact that one of the shoulders of the red plastic plug was not properly fitted over the spring. Nice.
For my next trick, I stretched out the paper filter to compare it side to side. Some poor planning on my part is evident here. Ideally, I should have stretched it out on the floor and taken a picture. Problem is it was mid-day and our floors REALLY needed to be vacuumed, what with having 3 dogs laying around. So I pinned them and stretched them out on the cupboard door instead. Glad I did too, because it shows what a fine finish you can get if you use good paint, a good brush and a delicate stroke. Some people ask if those cupboards were sprayed, but if you look carefully you will see very fine brush marks. I'm really proud of those cupboard doors.
Anyway, problem was that they weren't quite tall enough for a side by side comparison of filter paper. Here's the scoop... the Fram is the ONE piece on the left: 150 cms long. The two pieces on the right are the Bosch; 150 cm & 90 cm for a total of 240 cm.
So, taking into account the overall width of the paper, 9.5 cms for both, I end up with a dramatic difference in surface area:
Fram: 1425 cm2
Bosch: 2280 cm2... 60% more surface area!
Another thing that's noteworthy: When I was stretching the filters out, I had to be careful to not tear the Fram. Even being gentle, it started to tear at the pleats in several places:
So there you have it. The Fram filter is probably just fine, so long as it doesn't plug up 40% earlier, the paper isn't torn, and the bypass spring and plug aren't messed up.
Further discussion on the PelicanParts forum
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