General Oil question

[PointFiveO]

Recently I was removing the makeshift tubing that connects my air filter housing to the top of my carb intake (see attached pic) with the intention of measuring the diameter of the tubing in order to replace it. Anyway while I had it disconnected I noticed a lot of black oil in the tube and on the the part of the carb intake cover that was connected to this tubing. It made me wonder if this oil might be getting sucked into the carb. I was quite alarmed as the engine was fully rebuilt just last year. My question is how much oil coming through here is normal or acceptable and if mine is excessive what could be the cause of it. Obviously I have the oil breather tube connected from the valve cover to the air filter housing and it is fitted with one of those oil catch thingies. The air filter was new last year as well although I haven't yet opened the housing to check the state of the filter.

Regards,

Colm.

 

[Luxe]

Same issue here. I have changed the oil filler cap and the air cleaner has no oil on it, but the tube is misted with oil. Driving at 90km/ph for an extended period of time makes the engine smoke, so I am curious too.

 

[Luxe]

15w40 is what I was using btw.

 

[dragonwagon]

Use an old fashioned straight SAE30 - there will be less misting at high temperature with that and change every 1500 miles. Worked for me when I ran a 500 for a decade and 100,000 mikes.

 

[fiat500]

In common with many engine types, the Fiat 500 is designed to scavenge excess oil vapour from the rocker cover through the smaller pipe. This is directed into the pre-cleaned air at the centre of the air cleaner and should present no problem in normal states of engine wear.
The helical mesh device is not a filter but a flame-trap and as far as I know this is to prevent the potentially explosive situation if a backfire made it as far as the air cleaner from the carburettor.
There is a lot of oil vapour pressure in the crankcase with two pistons up and down simultaneously so it's not surprising that a lot of residue should be found in the smaller diameter tube. But if there is really a lot of it in the big tube that could be a sign of a worn engine, too much oil, too thick an oil, too thin an oil or an overheating engine.
Your level of contamination does sound a little excessive though.

 

[Bambino]

As stated above, all engines suffer from what's called blow-by where unburned fuel and air sneaks down past the rings and appears in the crankcase. As the crankcase becomes pressurised during the inlet and power strokes, that gas makes its way up to the top of the engine via the pushrods. It will be hot and will pick up whatever oil that has been splashed up as a result of top end lubrication.

The resulting mist is usually recirculated to the inlet manifold through a positive crankcase ventilation (PCV) valve that only lets gas flow when the crankcase pressure is higher than the manifold pressure (this pressure differential changes with rpm). This setup was a very early attempt at pollution control.

In the 500s, the vapour mist is returned to the air inlet proximal to the filter rather than the manifold, so a PCV valve is not really necessary, though a rudimentary one might exist as a spring loaded diaphragm in the oil filler cap. Simpler and easier though you might go through a few air filters. So yes, you will normally get oil and fuel (hence the flame trap) in that hose.

In your case and if the engine is performing OK, I'd just clean the inlet hoses, check the air filter, check the crankcase oil level, maybe change to a slightly heavier mineral oil (these motors are not designed to run on modern synthetics), say a 20W40 or 20W50 and monitor the situation.

My 2c,
Chris

 

[PointFiveO]

Thanks guys for the responses, I knew that it was designed to recirculate the oil blown off via the breather tube but was unsure how much oil was 'normal'. As the engine was rebuilt last year I would presume it's not worn. I do also use a mineral oil for classic cars. Maybe the oil level is a little high or possibly as it's running on the rich side some unused fuel has washed down the barrels to thin the oil (?). I suppose I hadn't previously removed the tubing so didn't expect to see dried looking oil as far as the edges of the air intake on top of the carburettor, it made me wonder if it could be getting sucked into the carb risking a blockage. I think really it wasn't so much the quantity of oil as the distance it was travelling. Anyway thanks again, maintenance and regular cleaning seems to be the key!

Cheers,

Colm.

 

[Bambino]

Sorry Colm - I didn't mean it to sound like a lecture.

I've just checked my breather and there is a thin film of oil coating the recirculation hose - similarly with my old Alfa. I use a 20W40 mineral oil in both cars.

Cheers,
Chris

 

[PointFiveO]

No worries Chris, it didn't sound like a lecture and I'm always glad to glean what information I can from the more competent and knowledgeable members of the forum even if my limited mechanical experience means I don't always understand what I'm being told!

Thanks again,

colm.

 

[Luxe]

So this is odd. My Italian friends said to use 15w40, the newer manuals say to use Castrol 5w20. One user on this site says use sae30 straight up, but two others say use 20w40. So the big question is. Which oil is the best to use for worn engines?

 

[Bambino]

My understanding is thus -

Oil viscosity changes with temperature being 'thicker' at lower temperatures and 'thinning' out as temperature rises. It is assessed using an instrument called a viscometer (try saying that after a few drinks) which works by timing the flow of oil through a grid of holes at a particular temperature (usually 100degC). A rating is assigned and ranges from quick transit times ('thin' oils = low number) to slower times ('thick' oils = high numbers). An SAE10 oil will traverse the viscometer faster than an SAE90 oil.

An oil with a W in it just means that its been tested at low (Winter) temperatures and its viscosity graded against the usual temperature test. So a 5W30 oil will be 'thinner' than a 10W30 at low temperatures but both will have the same viscosity at high (engine) temperatures. If your engine is very cold on start up, it is an obvious advantage to be using a 'thinner' oil until it warms up to operating temperature.

The final thing to realise is that oil viscosity does not fall into neat categories but comes in continuous ranges. For example, you may have one that grades at 24 and another at 26 by viscometry, but if the cut point is 25, the first will be categorised as an SAE20 and the latter as an SAE30 even though they perform very similarly.

So which oil should you use? If you live in a cold climate go for, say, a 10W40 whereas if you live in the subtropics like I do, then a 20W40 will be OK. An SAE30 oil is equivalent to any #W30 oil - it just hasn't been cold tested - and I reckon that the squabble between a #W30 and a #W40 isn't worth entering into. If you have a worn engine you may be better off with a 40 rather than a 30, but please don't use a 90 ...

After all of that, I reckon that the most important aspect of this for us is to use a good quality mineral oil and not a semi-synthetic or full synthetic oil. I use Penrite oils because they are Australian made 'for Australian conditions' and I know the Managing Director. He's a good bloke and his company makes good oil. Synthetic oils are for modern engines that run much closer tolerances than our old clunkers.

The manual gives a range depending on ambient start up temperatures and I've attached the relevant page.

Phew - sorry about another lecture - hope all that makes sense,
Chris

 

[Luxe]

Anyone tried running some lamp oil i.e. Kerosene oil in their oil on start up? My Dad used to put lamp oil in the regular oil and start the vehicle and let it idle for 5 minutes. Je claimed it cleaned out deposits and passages. He never drove wwith the kerosene in, but after 5 or so minuts would turn the car off and drain the oil. I was contemplating doing this as I am pretty sure the engine oil ports need a good cleaning.

 

[fiat500]

I wouldn't do that with kerosene. You can get flushing oil which will do that job. Using modern detergent oils changed regularly, the engine should eventually be clean as a whistle inside, at least in the places which are critical. Just be sure to keep cleaning the oil filter too.

 

[looigi]

Hi All,

I would like to throw my two cents in here.

First of all, a bit of qualification. I am an aircraft engineer who used to work for an oil company. Having said that, I don't want any one to think my word is gospel. Everyone has an opinion on oils and everyone is 'right'..... for a given value of 'right'!

Modern oils have viscosity (thickness) modifiers in them. The easiest way of imagining what these look like are microscopic coils, they look like tiny little springs. These little springs expand with heat and try to maintain a more even viscosity as the oil heats up. The advantage here is that you can have an oil that is not too thick when the engine is cold, but will still provide good lubrication properties as the oil and engine heat up. Modern oils also have a lot of other goodies that reduce friction and detergents to clean the engine. I used to run diesel oil in all my old vehicles because the high detergent levels used to keep the sludge levels down.

Old oil was what is now known as monograde, like for example the old SAE30. A lot of these oils are basically straight oil with minimal or no goodies added. They are thick as hell when they are cold, and like water when they are hot.

I have seen people claim that "Aeroplanes are air cooled and they run straight monograde oils, so it must be good oil". The short answer is..... No! All aviation products have to be certified. The cost of certifying a new product is huge, so if a company has a product that is good enough, and it is selling, why change it? The upshot of this is that for low volume products like piston engine oil, they are still using the same oil great granddad did. Also aircraft engines have an oil change every 50 hours, so in mosy cases it never even gets dirty! A few multigrade semi synthetic oils are starting to get popularity in the aviation world but the uptake is slow.

Interestingly the only engine that I would not recommend multigrade oils for are radial engines. The old DC3 I look after still use a straight W100 (the W indicates antiwear additives) monograde oil. The crankshafe arrangement of a radial engine tends to break the little viscosity modifying spirals I mentioned earlier up and destroy them making the oil too thin. W100 is like treacle on a really cold day, and it is normal to get oil pressures in excess of 100psi just after startup when the oil is cold. It sometimes takes 30 minutes or so of idling to bring the oil up to the minimum 40 degrees before you can even run the engine up. Mind you, there is about 100 litres of it in each engine!

Sorry for the long winded post, but my recommendation is to use a good quality multigrade oil. oil technology has come a long way in even the last 20 years, take advantage of it!

Chris

 

[Bambino]

Hi all,

This is what I use in my old cars (1957 Alfa, 1967 Fiat, 1970 Alfa), Classic Light Engine Oil - it's a multigrade mineral oil. Nominally 20W60 but also graded as 20W40. If they don't stock it, I use Penrite HPR30. Hope this is OK ...

No affiliation to Penrite.

Chris (the serial pest)

 

[Luxe]

Did my first oil change today and oh my lord I wasn't prepared to see the amount of accumulation of build-up in the oil slinger. I pulled the plate off from the oil slinger and the inside of the slinger cavity did not look like the photos I have seen. It was a solid wall. I ignored it and started cleaning the plate. I looked better at the plate and took a screw driver to it and the amount of material that came off it blew my mind. I then started looking inside the slinger and took a screw driver to it as well. Attached below is most of the material I got out of the slinger and face plate. How and the heck was the oil even circulating to the slinger?

 

[Vitesse]

Is that a normal size bucket? I don't know what size a normal bucket is, is it a gallon?

If so are those chunks of metal in there?

Tony

 

[Bambino]

Is it possible to fit a proper full flow oil filter to these engines and if so, where do I get all of the bits required? I don't need a cooler.
Chris
PS: I'll answer my own question - yes it is and Nanni Ricambi in Bologna stock the bits but never answer email enquiries ... frustrating
So I guess to rephrase, where else can I get the parts or who will sponsor me to fly to Bologna?

 

[Luxe]

It is an oil pan about 4 inches deep. The material was oil gunk and metal filings. That is why I want to do a compression test to see if I need to do a rebuild. It is a 45 year old engine.

 

[Vitesse]

Don't quote me but I think you are looking at anything above 100psi as being regarded as ok. Those bits of metal would concern me though, as they have obviously concerned yourself. Somebody else maybe able to confirm though?

Tony