will it do any harm using 5/30 oil in my A-4

[joe_db]

The problem with oil for gasoline engines is the additives and viscosity are *totally wrong* for an Atomic 4.
We do not have an engine made with tight tolerances that likes very thin oil like 0W20, 5W20, and so on that is often specified for modern cars. IMHO these oils are even a bit thin for a car, my car asks for 5W20 and the exact same engine internally in the turbo version specifies 5W30. I use the latter at a sacrifice of maybe half a MPG.
Speaking of MPG, corporate fortunes are not won or lost on eeking one more MPG from an A4 The anti-friction additives in modern car oil are not what you want with a wet clutch!
We also are lacking in catalytic converters. Zinc is good for old engines, but it will poison a cat. Taking zinc out is bad for our use. Our local shop sells a high zinc oil for old muscle cars with no emission controls, which I thought was perfect for an A4. Turns out not, it did not seem able to hold the set pressure well. I went back to Shell Rotella 15W40, which IMHO is one of the better oils you can use for an A4. We also no longer need to fear multigrade oils. I remember back in the day air cooled Porsche drivers and pilots both were highly suspicious of multiweight oil, it was assumed the wider the viscosity range the more likely the oil was to break down. That has not been true for quite some time except for Detroit Diesel engines, which for reasons I do not know absolutely do not want any multigrade oil anyplace near them.

* cautionary tale about new oil and old tech: Continental decided to spec Mobil 1 in one of their aircraft engines. It sure made cold starts easier, but in the end it was wrecking the engines because no one at Mobil had ever thought about engines with more blowby than any modern car that ran on leaded 100 octane gas. The oil was not able to deal with the lead. Remember when the A4 was designed, oil was almost straight out of an oil well with the lighter fractions boiled off and a handful of zinc thrown in

[Administrator]

That has not been true for quite some time except for Detroit Diesel engines, which for reasons I do not know absolutely do not want any multigrade oil anyplace near them.

I wonder if this ties into the commonly held view amongst the oldtimers in our firehouse: "If you see oil leaking under a Detroit diesel (in the FH), you don't worry. If you DON'T see oil leaking, THAT'S when you worry."

Bill

[Sam]

My two cents based on owning a 1966 early model A4 for 44 seasons without needing a teardown or rebuild. [1] Picking up on Neil's comment on oil being the lifeblood of the engine [especially w/out a filter] I change oil for spring launch, mid season and fall /winter layup. [2] I use any quality name brand detergent oil that is on sale 10w -30 or straight 30w. The 10-30wt is 30wt at summer temps. [3] Engine sits at about 5 degree angle in the boat at the dock calling for 4 - 4 3/4 qts of oil. I use 4 qts oil and 1 pt STP which is very thick viscosity and loaded with zinc. It blends in to the oil raising the end viscosity to some unknown level.

The point that has not been mentioned is that the higher viscosity numbers wheather it be 30 or 40wt oil "adheres" more and longer to metal components during non running times. During the season hopefully I use the boat once during the week and twice on weekends. Sometimes due to weather/conditions it sits for a couple of weeks. Like to think startup wear is minimized with the thicker viscosity oil.

[Shrek]

choosing the right oil

had a conversation with our marina shop parts clerk who is a retired chief engineer (unlimited) He told me exactly what sam has said regarding the film thickness of the heavier oils which clings to the parts after they have stopped moving. This protects the parts on the next start up. What I cannot get my brain around is how it does this in a multi viscosity oil which is, say 10 when it is cold (the oil is cold, not the weather) and only 30 or 40, when the oil is hot. Why does it coat with a film after the engine cools down? It seems from the earlier poll results that most prefer 30wt detergent oil and not multigrade, so which oil is the best for zinc. Is there a poll for the best brand for the A4?

[Sam]

All right - I am a long retired engineer who spent too much time in management so I appreciate the knowledge from "hands on" types. I am going to get a headache here trying to remember 50 yr old book learning.

- 5w-30 oil used in late spring/summer/early fall is 30wt oil. When the A4 gets to operating temp 140 F to 190F depending on your set up the oil [any oil[ will get somewhat thinner just from the higher temp. [compare changing your oil when engine is cold vs warmed up]. During the season the oil is never the 5wt The "w" in 5w means "winter" or cold. [don't know the benchmark temp]

- the "5" or the "30" represents how many seconds it takes for one oz of oil to go through a vicometer. The multi grades or straight oils is the result of varrying complex interactions between viscosity modifies and chemical solvents added to the base oil. The additives keep the multi grade oils from thinning out too much when warm. Straight 30 is more oil % and less modifiers and generally a slightly better lubricant.

- the old universal A4 manuals [engineers] call for SAE30 detergent oil. It is true back in the 60's multi grades weren't around but they could have spec'd straight 10, 20, 30, 40, 50 etc? What I assume they did do was consider oil psi [about 40], amount of oil flow through passageways, oil shearing capability at shut down ie "clingingness" [if that is word] especially on bearing journals, cylinders and volume of oil in the sump. The initial flow of oil at start up was based on the expected sailing climate temps- generally warmer months.

My bottom line from this trip down memory lane is I think you would be ok with your initial Costco oil purchase. In season or warmer climates SAE30 or a multi grade to 40wt I think is fine. There is a tradeoff between the chosen oil adhering to metal parts at start up [thicker is better] and how fast oil flows to the parts [thinner is better]. For an older good running A4 that has some wear probably using a multi grade up to 40 wt is a good bet. Just change it often.

[Shrek]

Now it all makes sense

Thanks for this very enlightening information. So ambient temperature dictates the thickness of a multigade oil at startup. I am thinking about Rotella T4 15/40 or would 30 weight still be a safer choice given the fact we only have a crankshaft with 2 main bearings. I feel like I am asking a lot of questions but ever closer to a final decision thanks to our knowledgeable followers - thanks to all who have chimed in so far.

[joe_db]

Both 30 weight and Rotella 15w40 have been used with success, so I wouldn't say either one was a bad choice.
Bad things oil can do:
1. Be too thin when hot. If you can't hold pressure when hot, your oil is getting too thin or your clearances have got too big for any oil to work.
2. Be too thick when cold. This makes the engine hard to start and makes the oil pressure too high when cold. This is hard on the oil pump and despite the high pressure reading, the oil may not be circulating well.
3. Be too slippery. Our engines have wet clutches. Too many anti-friction additives and they will slip. Motorcycles also have wet clutches and you will see a special line of Mobil 1 synthetic and Amsoil synthetics that are designed for wet clutches.

Neither 30 or 15w40 Rotella should have any of these issues in the summer, straight 30 might be a bit hard to start in winter.
* speaking of winter, when I start my engine I let it run at idle until the oil pressure settles down some.

[ndutton]

MMI Manual: 30wt or 10-30 oil
Robert Hess: 10-30, 10-40 or 15-40 oil, SJ or CH-4 rating

Notice that neither mentions weights lower than 10.

[Shrek]

Final decision on what oil to use.

Despite the thought that up to a 40wt oil should do no harm to my A4 I have decided to stick with the straight 30 wt oil regardless of the cost.
My engine is probably 1972 - same year as the boat (Columbia-30) so I need the assurance that both ends of the crankshaft remain lubricated. The trade off, I suppose is that the thicker oil might have gone some way towards less blow-by as it might have given a better seal at the piston rings.
A major motor repair would cost way more than many oil changes.

Also simple logic in reading the poll of the owners and its results, shows that the majority are using 30 wt with detergent and that is the basis of my decision.

Thanks all for this lively debate on oil - I am sure this gets revisited almost annually.

Regards - Gordon.

[Shrek]

one last question - Sorry

As I have an oil filter on my A4 should I be using only non-detergent oil in the engine or does it matter either way?

I.e. If I use a HD High detergent oil, does this prematurely clog my inline filter ?

[romantic comedy]

detergent is very important!! Yes use detergent oil. The detergent oil helps to suspend particles so the filter can remove them from the oil.

[Shrek]

Managed to find Pennzoil sae 30 and picking it up today - $6.67CAD per qt.

[Mo]

Solid on 15w40 diesel oil

15W40 diesel oil is what I've used for 13 years. No adding oil between oil changes even running hard in chop off NS. FWIW. I think I was the first to use it and post it's benefits to the forum...Since then loads of others have tried it on the forum here and there are a couple of things.
-no, it's not going to bearing wear. It's actually better and has better shear qualities.
-you will "use" or "burn" less oil under constant load driving into weather.
-it has higher zddp...and in old engines that is a plus
-it has high detergent levels.