Top bypass

Roger · Mar 1, 2003

I haven't found much about this topic when I searched. How important is a top by-pass valve on an oil filter versus one located on the bottom of the filter?

A top by-pass valve reduces the possibility of oil flowing back over the dirty side of the filter if it goes into bypass. This seems like a fairly important thing to consider when selecting filters. But there are so few filters with the top by-pass design. I've only found Motorcraft and Wix made models with them.

Pablo · Mar 1, 2003

Well actually other companies make them. (Amsoil/Hastings/Baldwin)

Often discussed. Do a search. Ford says must have.

Try this:

My post last year on "Top by-pass"

Greaser · Mar 2, 2003

Pablo...I just purchased a Bosch Premium oil filter and by looking in the thing can't see the by-pass.They claim from their web site it's a "clean side" by-pass,but where is it?It doesn't seem to be at the top of the can like 98% of oil filters,and I can't really see it at the bottom like my Mobil.May-be I'll have to wait and cut it open after my next oil change to find it

Roger · Mar 2, 2003

Pablo, thanks for the post. It confirms my instinct that this is an important feature to look for on a filter. I for one could never tell if a filter went into bypass, but if it ever did, the idea of washing stuff back into the engine that the filter caught once isn't to exciting.

I'm just surprised it isn't a more comon feature.

JPowers · Mar 3, 2003

quote:

Originally posted by Greaser:
Pablo...I just purchased a Bosch Premium oil filter and by looking in the thing can't see the by-pass.They claim from their web site it's a "clean side" by-pass,but where is it?It doesn't seem to be at the top of the can like 98% of oil filters,and I can't really see it at the bottom like my Mobil.May-be I'll have to wait and cut it open after my next oil change to find it

The Bosch Premium used to have a spring bypass, but the design was changed. According to the person I spoke with at Champion Labs, the bypass in there now is more of an on/off switch, rather than a gradual bypass using the spring type that the Mobil 1 and K&N still use. Although this may be a cost issue, the cheaper bosch filter

still uses the spring! Champion tried to tell me that the new design is better and that he uses the Bosch Premium

on his cars. If this is so, then why would the more expensive K&N and Mobil 1 filters use the spring? Look at these 2 charts from Bosch's website. The one for the Premium filter doesn't list a bypass valve.
STANDARD FILTER

PREMIUM FILTER

This is the main reason I don't buy Bosch filters anymore.

[ March 03, 2003, 11:11 PM: Message edited by: JPowers ]

RalphPWood · Mar 3, 2003

It doesn't mean much on a modern engine. Years ago large abrasives would accumulate at the bottom of the filter. When the bypass valve opened it would flush the large stuff into the bearings. Modern engines generate a lot of abrasives. We call engine wearing abrasives that can only be removed by draining the oil or using a submicronic bypass filter. A modern engine doesn't generate much that is large enough to be removed by the almost useless full flow filter.

Ralph

Roger · Mar 3, 2003

I've found that the existance and location of a bypass valve seems to vary by model within a manufacturer's line. The cross reference filters for my Nissan have 2 arrangements. The mobil 110 and Bosch 3323 clearly have a bottom located spring valve, while the Wix 51356 has the top located valve. On my Ford van however, the mobil 301 has a top bypass valve just like the Motorcraft FL-1A. But I can't even see a bottom valve in the Bosch as you can with the 3323. Go figure.

Ralph, if you are right, that's the best explanation I've heard yet for the absence of this design. In theory, it seems to me to be very important and a better design. But, with the exception of Ford, no one else seems to worry about it. It may simply not be needed that much anymore.

Greaser · Mar 3, 2003

Well I'm sure if a by-pass is needed for a certain application Bosch(Champion Labs) will put one in the filter.We just haven't seen it yet.I'll cut one open after my next oil change and find it.Ralph...If the automakers didn't need to install a filter on an engine..they wouldn't...try running your car with-out one and the do a oil sample test.

RalphPWood · Mar 5, 2003

quote:

Ralph, if you are right, that's the best explanation I've heard yet for the absence of this design. In theory, it seems to me to be very important and a better design. But, with the exception of Ford, no one else seems to worry about it. It may simply not be needed that much anymore. [/QB]

Roger,
About 40 years ago I read why they put the valve in the top. It made sense to me and it stuck. I wouldn't use a top relief valve on my Toyota Camry that is tilted downward.
Back in the 60's I was putting a submicronic bypass filter on a tow rig for a racing company. They were sponsered by Chevrolet but the filters were supplied by Baldwin. The racing oil was supplied by Valvoline. They gave the Baldwin filters to a guy they knew that had a gas station they used. Ford Rotunda filters in the dragster. They wanted the relief valve in the top of the filter.The Rotunda was the same as the Motor Craft of today.

Ralph

Top bypass

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