What kind of motor oil do you use?

[hanleyclifford]

After my partial rebuild early spring 2015 & having done at least 6 serious lil system flushes, I adjusted the oil pressure bypass in because i was seeinf pressure holding at about 25 - 30 lbs. After the adjustment I saw 35-40 lbs. Then I drained my last clean oil , something cheap and common, 10-30 and filled her up with 15-40 Rotella. Did a few more odds and ends which allowed the engine to cool down and give her a start.
The start up pressure shocked me at 70lbs right off the bat. Then quickly drolped to 60. I thought I waz going tl need to adjust the.pressure down. However, after warming up the pressure dropped back to hold.between 30-40 under normal opperation .
Obviously 60-70 is way too much but Im now wondering if opperation 30 & 40 is ok.

Bill - That 15-40w Rotella is rugged stuff and may not be ideal for many members. Choice of oil has a lot to do with engine condition and how you use the boat/engine. I use the Rotella because my engine is worn and loosey-goosey and I run my engine all day at cruise often as many as 12 hours at a stretch. I need the Rotella to maintain 40 psi without having to crank in the relief valve. Weather is also a factor. If I have the engine running in winter I go to 30w or in the case of last winter as low as 5-30w. Next year I will have a different engine and will probably run straight 30w if the tolerances are anywhere near spec. Right now I'm running .016" crankshaft end play and rod side play .008", both way over spec - and the bearings are right at max spec except for the cam bearings. If my engine were human the diagnosis would be internal bleeding. Rotella keeps me stuffed and quiet.

[JOHN COOKSON]

I'm thinking the only way to be sure of correct oil pressure is to install a new gauge and matching sender.
Catalina Direct has a nice oil pressure gauge which matches the fuel gauge I installed last season, but the sender is metric thread.
Will any sender work?(Maybe)

John
You answered your own question. The sender and gauge must be matched (ie from the same manufacturer)for accurate readings.
That having been said some sending units and gauges are interchangeable because they have the same parameters. If you know the manufacturer of the sending unit and gauge you might be able to cross reference.

TRUE GRIT

[joe_db]

Not exactly.
If the sender and the gauge are both the same range and both the common 240-33 ohms, then they should work fine together. I went through 3 gauges on my old engine with the original sender and they all worked fine. Nothing wrong with getting all new though if you are not sure what you have. Remember 33 ohms is full scale, so if you have a 100 PSI sender and an 80 PSI gauge your readings will be off.

John
You answered your own question. The sender and gauge must be matched (ie from the same manufacturer)for accurate readings.
That having been said some sending units and gauges are interchangeable because they have the same parameters. If you know the manufacturer of the sending unit and gauge you might be able to cross reference.

TRUE GRIT

[hanleyclifford]

Nothing wrong with using an electric gauge and sender but I would never rely on it alone. Keep a second, direct read gauge hooked up somewhere on the engine for comparison purposes.

[romantic comedy]

A mechanical gauge can be mounted most anywhere. There are tubing kits 15 feet long available.

I hooked one up on my VW bus. It was on the dash. I bled the line and had oil right at the gauge. It was very sensitive, and would go up and down when I shifted.

[hanleyclifford]

FWIW

I had a mechanical gauge on the panel for a while fed by a long plastic "kit" tube. The plastic hardened and deteriorated over time and broke off right at the ferrule. Lesson learned: use copper for the run to the gauge.

[Sam]

I have virgin early model A4 and have always had "mechanical" oil pressure gauge with connected copper tubing w/compression fittings. Gauge is on cockpit wall exposed to weather during the season. Am on my 3rd gauge in 42 years with same 3+ ft tubing [tee'd off to OPS]. Used Stewart- Warner gauges, sometimes a little hard to find "mechanical" type. FYI, engine is on slight aft tilt and have always used 4qt name brand 30W or 10-30W w/ 1 bottle of STP. Oil pressure is about 35psi at start up, 30+ psi at cruise and around 20psi at idle. Once in a great while I get a very small leak with this set up and a fitting needs a little tightening. I believe you get a accurate reading with the mechanical gauge vs electrical and matching the right sending unit.

[ronstory]

Apologies for resurrecting an old thread.

We have had other members report that oil pressure increases with time and temp increase after start up. I have tried to make sense of this because it is counter intuitive to my understanding and experience that viscosity decreases with temp and hence pressure should also decrease. One factor that keeps coming to mind is the nature of the oil pump intake. The "bottleneck" is the 1/8" NPT 90 degree street ell coming right off the oil pump. Since that fitting is a casting, it's cross sectional area is subject to the irregularities of the casting process. Even a small burr in the oil stream could have an influence on flow especially at cold temperatures. Because of the foregoing "theory" I have modified my oil pump to use a 1/4" NPT fitting. The difference in oil flow was impressive and could account for the big pressure differential I live with between start up and cruise. I live with it and enjoy the (relatively) massive flow and pressure increases as well.

As a person about to assemble a rebuilt A4 engine after the last one lasting 45 years... I will hopefully be dead before anyone needs to rebuild it again.

I sent off the oil pump to MMI (courtesy of the Amish ones ) for testing and the result are it landed on the 'correct' side of the bell curve. But looking at Hanley comments about reducing the inlet restrictions and the 1/4" NPT street Ell... has anyone else done this?

BTW, when I build my first custom car, I did a "high volume, standard pressure" oil pump on the blueprinted engine. It has been a great motor, no leaks and still lots of pressure (75 PSI cold, drops to 40 PSI hot at idle and 50-60 PSI when running through the gears. Is a similar performance (but not exact PSI) possible on an A4?

... this is coming from a person after two A4s with low oil pressure after 2-3 hours of cruise.

[joe_db]

Apologies for resurrecting an old thread.



As a person about to assemble a rebuilt A4 engine after the last one lasting 45 years... I will hopefully be dead before anyone needs to rebuild it again.

I sent off the oil pump to MMI (courtesy of the Amish ones ) for testing and the result are it landed on the 'correct' side of the bell curve. But looking at Hanley comments about reducing the inlet restrictions and the 1/4" NPT street Ell... has anyone else done this?

BTW, when I build my first custom car, I did a "high volume, standard pressure" oil pump on the blueprinted engine. It has been a great motor, no leaks and still lots of pressure (75 PSI cold, drops to 40 PSI hot at idle and 50-60 PSI when running through the gears. Is a similar performance (but not exact PSI) possible on an A4?

... this is coming from a person after two A4s with low oil pressure after 2-3 hours of cruise.

Running Shell Rotella 15w40, I get 60-80 on a cold start and it soon drops down to 40. I could set the pressure higher, I have the external oil filter with the pressure adjustment, but 40 was my goal. It is pretty much rock-steady on 40 unless run very long and hard, in which case sometimes it can drop to 20 at slow idle.
You may want to look at an oil temp gauge and an oil cooler. The temp gauge is on my list and maybe a cooler depending on what I find.

[ronstory]

Joe--

I wish had your oil pressure, then I would only be dealing with a bit of blow-by. I manage that by having vent cap with a hose connection that I put in the bilge blower inlet. Looks similar to:

https://www.napaonline.com/en/p/BK_7354387?cid=paidsearch_shopping_dcoe_google&gclid=Cj0KCQjwpLfzBRCRARIsAHuj6qVWQE5-YPrsrIIY4xMEFMPrxUQmJCr2LmRogLbbcq1FbTlo7OZUUQoaApyvEALw_wcB

I have 80PSI cold when warm up the engine and drop to 40-45 in 5 mins. When running for more than hour at cruise I'm at 20 PSI. At idle when I'm maneuvering into the slip, I'm at so low on oil pressure that I'm worried about the OPSS killing the engine.

Now back to the question: Has anyone else done the larger 1/4" NPT Street ell into the oil pump?

[joe_db]

Joe--

I wish had your oil pressure, then I would only be dealing with a bit of blow-by. I manage that by having vent cap with a hose connection that I put in the bilge blower inlet. Looks similar to:

https://www.napaonline.com/en/p/BK_7354387?cid=paidsearch_shopping_dcoe_google&gclid=Cj0KCQjwpLfzBRCRARIsAHuj6qVWQE5-YPrsrIIY4xMEFMPrxUQmJCr2LmRogLbbcq1FbTlo7OZUUQoaApyvEALw_wcB

I have 80PSI cold when warm up the engine and drop to 40-45 in 5 mins. When running for more than hour at cruise I'm at 20 PSI. At idle when I'm maneuvering into the slip, I'm at so low on oil pressure that I'm worried about the OPSS killing the engine.

Now back to the question: Has anyone else done the larger 1/4" NPT Street ell into the oil pump?

Bearing clearances? Have you measured the oil temperature? You might putt off a rebuild with an oil cooler and maybe thicker oil.

[ronstory]

Could be bearings clearance or it could be the oil pump. Ken's thoughts were that pumps do go wear out.

I already installed an indigo remote oil filter plus their oil cooler in an attempt to stave off the rebuild. I'm also using the Indigo thermostat, so I have nice toasty and consistent 180F water temp with their electric FWC.

So I'm heading down the rebuild path on the spare motor... and trying learn as much as possible about 'best practices' from the forum. I have all the MMI tech tips archived, but looking for do's & don't from our very knowledgeable members.

... and I will make positive to install all three internal oil plugs.

[Mo]

Been using 15W40 Diesel oil for 13 years now. Have not had one mechanical issue with the engine...3 black iron hot exhausts later, a fuel pump, bunch of filters, generally maintenance and a raw water pump. I've changed the oil at 25 hrs and to be honest it's hard to see where it is on the dipstick it's so clean...been clear for years now. Been a good engine. Still a great running engine.

EDIT: The engine developed a head gasket leak (air only) under the T-stat area where the head was weakened from years of salt water running through it. When the gasket was changed I couldn't get to torque two studs and found a small crack near the exhaust ports between two stud holes...again, worn thin from years of salt water. I changed the engine out and put in my spare. The internals are all still good on that and I've been told the right guy with a brazing rod can fix that issue. The issue it experienced had nothing to do with the oil I use. 15W40 is in the new one I put in as well.