low oil pressure at low revs

[jwh20]

 

 

 

 

5W40 Full Synthetic

The owners and shop manuals call for 20W50 and some here suggest even heavier especially if you live in an area where it's hot.  Some have expressed concern about using fully synthetic oil as having a greater tendency to leak on some engines but I believe it's generally better for the engine than mineral-based oils.

 

I just recently changed the oil on my "new-to-me" 2002 LeMans and I ended up using some Castrol semi-synthetic 20W50 that I found on sale.

 

 

Now you're gonna send me back to the owner's manual, which is at home, to see what it specifies. I was pretty sure it called for 5W40, although it suggested a couple of other weight oils that were OK.

 

I've had BMWs for many years, and they generally call for 20W50, but I don't think that's what the LeMans manual said.

 

 

From the shop manual there are several options shown depending on your expected temp range.  But as I recall the owners manual calls for 20W50 as the "standard".  I don't think there is much difference under typical motorcycle operating conditions on the "W" side of these.  How often do you run your engine in sub-freezing temps?  Me?  NEVER!  So you're effectively running SAE 40 with your 5W-40.  Should be good as the 40 will get you to the top of the temp scale.

 

 

And here is what my Owners Manual says:

 

 

But after looking online, it seems there is some disagreement among the various printings of the V11 Owners Manuals on the correct oil.  Some do seem to say "5W-40" as yours does.  

 

In the end it probably doesn't matter much.

[Bjorn]

One more thing about the oil viscosity, i do know that the updated v11 manual specifies a different value than the first/original manual. Need to look it up.

[luhbo]

...  So you're effectively running SAE 40 with your 5W-40.  Should be good as the 40 will get you to the top of the temp scale....

Not really. The first value stands for the viscosity of the base oil, the second value relies on the quality of specific stabilisers/additives. That said, a 5W-40 indeed may be enough under normal conditions (especially in water cooled car engines), but then you shouldn't whine when at low idle/tick-over in combination with higher temperatures the pressure light starts to flicker. The more as the red light 'on' only says that the switch has contact, nothing about the reasons or possible consequencies.

 

BTW, I'm quite sure we already have a lot of oil threads in the tech section

 

Hubert

[jwh20]

I guess I heard this explained the other way around, namely that the 40 was the oil viscosity rating but the 5W was how it performed in cold temperatures.  So a 5W-40 was 40 weight but performed like a 5 when cold.  In other words it has enhancers to improve its low temperature viscosity.  But agreed, it's a complex topic and not really well understood by anyone except perhaps the folks at SAE or API...

 

I'm not an authority enough to dispute anything you said though.

[luhbo]

Me neither, that's what makes oil freds so entertaining

 

Hubert

[docc]

I think we should all dive in again anyway.

 

Be aware that vehicle manufacturers have long been under pressure to reduce fleet-wide emissions, lower fuel consumption across their entire range of production, and reduce waste product over the vehicle life. This has led to lower and lower viscosities, as well as longer and longer lubricant change intervals.

 

Do not believe for a minute that these changes are in the best interest of engine life or the satisfaction of the long term owner beyond the warranty period.

[luhbo]

You probably can't proof that, Docc. All my modern car engines over the last 20 years had done well over 250.000 km when the rest of the car forced me to get another one, the last two had over 320.000 even (PSA 2.0 litres, 140 HP). I never had a problem caused by insufficient oil quality.

Could be that things are a little different when we talk about air cooled big twins, usually operated with highly varying oil temperatures, with lots of short distance use and much stop-and-go. But even then this engine does 100.000 km easily.

I don't see any real need to grieve for outdated and poisonous additives. Any modern oil of good quality as mentioned in the manual will do it.

 

Hubert

[docc]

True, all of that. Yet, I take some instruction from the problems with my Jeep engine which has been made by Chrysler for twenty years while the oil was thinned more and more by specification changes leading to start-up knocking and increased oil consumption complaints. Simply returning to the early specification (thicker) oil has been a simple solution.

 

When I saw the change in the Moto Guzzi specification I assumed the same forces at work. Perhaps instead the later lubrication (underside piston spray) will only function properly with the thinner oil?

 

For a rider having flickering oil pressure warning while warm at idle, I would first be certain the idle is truly high enough. With tachometers that often overstate the tick-over, the oil pressure is not going to be happy below 1000 rpm.

[Bello]

I bought this bike, an '04, last November, and it had 10,620 miles on it when I got it. The previous owner had it since 2009, but had only put about 2600 miles on it in that span. However, he did change the oil twice, and kept the receipts of that work. Both times the oil he used was 10W60. When I changed the oil a couple of weeks ago, the mileage was 14,800, and I went with what the manual recommended (5W40).

 

So should I switch back to what was used previously? I don't see anything as thick as 60 weight recommended in jwh20's chart above.

[jwh20]

I think you're good as is.  If it was mine I'd leave the 5W-40 in there since that is what is in your manual and under the conditions you're likely to ride in around NC, that will be fine.  Plus tossing out $25 or $30 worth of new oil is not all that attractive to me at least.  

 

But I think generally the opinion is that a heavier oil is a bit better for an air/oil-cooled engine.  Of course if you go too think you end up with flow problems and that's counterproductive also.

 

15W-50 or 20W-50 are pretty common since they are types commonly recommended for Harley's so most bike shops have it or something similar.

[luhbo]

10W-60 is what Guzzi recommends in several shop infos. That's what I've been told, I haven't seen one of those letters. Tossing out 30$ of fresh quality oil just because of this would be beyond my imagination, too.

 

Hubert

[Bello]

OK, then answer me this. When I changed the oil, I first drained the sump, then pulled the filter cover and changed the filter. If I don't drain the sump first, will all that oil come out when I take the filter cover off? Or can I get the filter out (to check the seat of the o-ring) while leaving the oil in the bike?

 

By the way, guys, thanks for your attention to this.

[jwh20]

The oil drain and the oil filter access plug open into the same space.  You may not get all the oil out through the oil filter plug but you will get most of it:

 

 

It has a lip around it so it won't drain all the way to the bottom.  #32 is the oil drain plug.  #29 is the oil filter cover.  So there might be a quart or less left in the bottom of the sump that won't drain and perhaps 1/2 qt. trapped in the filter itself.

[luhbo]

...If I don't drain the sump first, will all that oil come out when I take the filter cover off? ...

Yep. All at once. The preferred method for endurance racer you could say

 

Hubert

 

BTW: working through this manhole in my opinion is the main reason for all those loose oil filters. Without the proper tool to correctly tighten the filter you're on a steep slope towards disaster.

[Bello]

 

...If I don't drain the sump first, will all that oil come out when I take the filter cover off? ...

Yep. All at once. The preferred method for endurance racer you could say

 

Hubert

 

BTW: working through this manhole in my opinion is the main reason for all those loose oil filters. Without the proper tool to correctly tighten the filter you're on a steep slope towards disaster.

 

I actually am accustomed to working with a filter mounted that way, because I've had several BMW K-bikes. The Brick motors have a similar setup, and the K-bike filter wrench also fits the MG filters. But since I'm getting the dash light, I have to check to see if I did it right or not.