Oil Grades !!!God its confusing.....

[garage dweller]

Hi All,
Sorry to dig this one up again but I'm confused big time.
Engine is a 1970 2.2 with Webber carbs on 87,000 miles
Bought the car three years ago, mechanic has always changed the oil. When I bought the car it was a dry engine, after the mechanic serviced it , it pissed oil. After querying him he says hes put in 5W40 semi synthetic. The car ran well if a little smokey until it got warm, same mechanic looked after it ..but recently I have decided to go it alone and do my own thing...
Research and my local Halfords suggested a 10W40 or 15W40 mineral would be okay for UK general driving, you guys talk about 10W40 to 20W50 so I figured its in the middle. I've duly done the change and put in 9 litres of Havoline 15W40. Theory being this should be okay for the usage and the heavier non-synth grade would help the sealing and reduce the oil being burnt due to better sealing characteristics. in the cylinder I've started the car after the change and the oil pressure looks high and the car doesn't rev as freely and was hesitant at idle/sound like it is running lean. I've increased the idle but the pressure is running at over 20psi and the temperature is up a little, not happy as this suggests the oil flow rate is down...any thought chaps asI am nervous about running the car at the moment????
Regards
N

[randywebb]

if there is a problem it cannot be the wt. of the oil you used

done anything else to it?

right amount of oil in it?

oil pressure too high would be very unusual...

[cygtoad]

I'm with Randy. The issue probably has nothing to do with the weight of the oil. You should see slightly higher pressures with an increased viscosity oil at startup, but nothing too dramatic.

How many bars are you getting on your oil pressure guage? You should see about 1 bar per thousand RPM's when the car is warm. I am not sure where you are getting the PSI reading unless our guages are completely different or you are using an externally hooked up monitor.

Is the engine running any hotter than normal? Are you hearing sounds that you haven't heard before? Are there noticeable changes in the color or volume of your visible exhaust? Changes in these areas would concern me.

[donstevens]

I agree with Randy that the oil is of no concern. That is a good weight for your UK climate. 20PSI at cold idle is fine. Let it get good and warm (100C) and then see what the pressure is. It will be down to normal.

You mentioned the car pissed oil when it was on a diet of 5W40 synthetic. Can you define pissed? A couple of drops? Puddle? Does it leak with the 15w40 mineral?

Reagrding the lean/idle/rev issues this is proabably simply a carb adjustment issue. Have a pro set them up and it should run fine.

Don

[Bill Verburg]

I can't comment on the specific issues you may be experiencing, but, when new that engine used 30wt dino all year round, by the late 70s early 80s, Porsche was recommending 20w/50 dino.

15w/50 synthetic was recommended untill faily recently.

latest rec. form Porsche is 0/40 synthetic.

If it were mine I would probably look for 15w/40 or 15w/50 either synthetic or dino. If I tracked the car or was concerned about either heat issues or very cold ambients I would lean toward the synthetic due to it's advantageous properties at both ends of the thermal spectrum.

[garage dweller]

Thanks for the advice guys, I feel reassured that no one has just yelled "NO!!" will get the car booked inand re-tuned.
Regarding Dons answer the definition of pissed is when it was first done I could see oil leaking out from under the garage door after parking up and leaving the car stood for four days. This thankfully slowed up but its still in the catagory of old porches don't leak oil they mark there territory!
Not had much time to do anything else over the last few day(work! damn) but I intend to have a good look this weekend, regarding other stuff no odd noises, I will check the tach/pressure relationship more closely and regarding exhaust colour volume seems about same but looks white-ish hence thinking it might be leaning out die to the added inertia/back pressure of the oil if the stuff the mech put in was uber runny.
Will keep you updated , thanks Neil