Mineral to Semi-Synthetic oil change

[bluebanana]

ive got a 4G92 which i have been putting mineral oil in the last year. The shop's 'lube guide' recommends that i use semi-synthetic and its around $10 more. I have read that changing can cause oil to leak from the seals, the problem is that the back of the engine head is leaking oil and now im worried if i get the semi-synthetic stuff that it will cause it to leak even more..is this true?? are there any other negatives changing to semi-synthetic and what do you guys think that i should do? Thanks

 

[milkandoj]

That a load of shit that old grandpas tell people lol.

The weight of the oil would have more effect than if its a semi syn. You could try a stop leak which swells seals to try prevent leaking, liqi moly or nulon make good ones. But if you are getting one that is just a thickener like all the stop smokes, better off getting the correct weight oil to start with. I know the liqui moly engine resealer worked real well on my mates 240z.

The semi syns are often mineral oil that have been chemically altered to have better shear properties and not break down as quick under heat. They also have better additive packages like more detergents and friction modifiers, so are a better oil as a whole, as higher in the range.

Probably go for a ___w60
Nulon street and track 25W60 could be the winner, in the orange bottle. As its nice and thick at start up to so less likely to leak when that cars off to.

If you want thinner at start up,
Penrite make two 60 oils, hpr 15 which is 15w60 and hpr 30 which is 20w 60, go the thicker on in your case.


What are you using now that leaking?
A 20W50 would be sweet for that motor that quite old and not leaking. But is its leaking you probably want thicker than a 50.
Maybe shell hellix hx7k (a 15w50)
Nulon 20W50 high kilometer. Bit thicker on start up. Prob better.
In your case stick with the 60's

 

[bluebanana]

thanks heaps..the engine has done 155 xxx kms and im using 20W50 and i was thinking of going to 10W40. I bought some of the Nulon stop leak stuff but haven't used it yet. Whats this weight of the oil that you mentioned and how does it effect the engine?
Thanks

 

[milkandoj]

If you say the back of the engine head is leaking, do you mean from the valve cover / rocker cover?
If so mate that a pretty easy fix and not worth using additives, buy a valve cover kit costs around 65 bucks, you get the rocker cover seal, spark plug seals and the half moon seal.
You get a hard rubber half moon seal in the kit and some people say you should buy the aluminum one that meek sell but i didn't.

Its all about sealing it right but its an easy and quick job. I can write another essay on how to do it if you like as i've asked others that have been doing it heaps as there's varying info out there on how to do it.

 

[bluebanana]

the rocker cover leaks but only a very very small amount. The mechanic said it was the head and i think they were referring to the cylinder head and it was around $500-$600 to fix

 

[trq-str]

Change to a semi syn and stick with the 20w50 viscosity you currently run (or thereabouts). There is no need for 10w40 in an engine which is getting up there in the k's department.

 

[bluebanana]

alright thanks, but what benefits will i get from switching to semi-synthetic over mineral?

 

[bazeng]

they SHOULD last longer than mineral due to all the additives etc.

Apart from that, not much.

You could stick with mineral if you want, there is really no harm except for more oil changes.

I know alot of old school V8 guys still stick with mineral oils over synthetic. Even some of the best engine builders / machiners swear by the mineral stuff over syn.

 

[EVO-00X]

The oil's main job is to lubricate and reduce friction between metal parts. Old school mineral oil is not the optimum for use in engines as it breaks down and loses its lubrication properties quicker. The simple fact is that mineral oil has been made obsolete by scientifically generated synthetics that are far more superior in lubrication and the reduction of engine wear. Synthetics can also handle lower and higher temperatures better than mineral oil - something those with turbo cars should take notice of. Those people who still stick with mineral oil for normal engine use are only kidding themselves IMO. If your engine is worn then stick with whatever oil has been used in the car to date, but once after a new build and seals etcl, go with synthetic all the way.

 

[bazeng]

The only thing is, in theory that is how it should be but in practice, evidence to those guys show that mineral oils are the ones to use.

They always tell me that the bores look better, the wear is better etc etc.

This is usually based on V8 motors which run much greater clearances than our motors.

 

[milkandoj]

Some report that fully synthetics can glaze bores, this has to do with the synthetic oil being so resistant to burning that it doesn't burn clean off. hence why you don't use synthetic in a rotary engine, it has to be able to burn off and a mineral oil isnt chemically bonded and wound as tight so it can burn easier.

But semi syns have part of their makeup as a synthetic oil and are generally made from a base mineral oil that chemically treated to make the carbon chains more resistant to breaking, many fully syns are made this way to.
Its the higher end fully syns that are completely manufactured, giving even greater control of impurities and the carbon chains formed, off the top of my head mobile one is an example, but you pay what $95 a bottle.

Plus like i say as they are higher in the oil range they have better additive packages, this is very important, they must have detergents to clean deposits, friction modifiers, chemicals to hold the solid sludge in suspension, anti coking agents, oxidation stabilizers.
From buying a $30 mineral to a $40 semi syn you get a better over all package.

My vr4 asks for oil as a minimum to meet SD, SE or SF standards, all mid range oils will be an SL or SM, so far exceed that standards around the time my motor was made. The cheapest shittest oil ive been able to find for sale these days is an SJ rating, but i wouldn't put that in my lawn mower lol. That still exceeds that minimum standard around then my motor was made.
Note; the S rating are for petrol motors and when they make a new standard for oils to be tested against and meet, they use a higher letter in the alphabet, so an SL is the standard before the higher SM was made. So SD, SE, SF are much lesser standards.


Then you can go to the fully syns but i feel that the older mitsi motors don't need it they last 300 000kms when the only oils were the more basic minerals anyway, so id rather pay $35-40 for an oil and change it every 4000kms (Funny number but i feel every 3000 is over the top and and like to do it before 5000, that just me, 5000's prob good
Plus our motors like to gunk the oil up with blowby soot, so why pay $95 for oil when that 5 liters sill has to be able to hold the same amount of soot in suspension as a mid range oil, so unless you change it the same intervals, you need the additives to work harder anyway.
So why not pay half the price for a good oil that you can change more often and clean it out. The earlier mitsi motors do not need such a high end oil.


I find oil such a fascinating topic to learn about, not many people even have an idea even at a lot of car shops, i like to think i know a bit but there so much to oil than it just being slippery and smelly.

 

[milkandoj]

The only thing is, in theory that is how it should be but in practice, evidence to those guys show that mineral oils are the ones to use.

They always tell me that the bores look better, the wear is better etc etc.

This is usually based on V8 motors which run much greater clearances than our motors.

That could make sense, look at rotary engines they need mineral as they must be able to burn it off. Even catrol edges 25W50 oil for big bore v8's isn't actually a fully syn like the rest of the range. Not that im saying edge is the bomb, just an example.

 

[bluebanana]

thanks heaps guys, i usually change oil roughly every 4500. What brand do you guys recommend and what grade should i be using? Ive been using castrol gtx2

 

[milkandoj]

Well you could try some shell helix hx7k, the high k one. 15w50.
Or nulon high km, 20w50.

Similar weight as what you had but better oil, With some liqui moly engine re sealer. That could help seal the leak, as it swells seals again.
Personally id keep the weight of the oil more suited and try an additive.

Or switch to a thicker oil to fix the problem, nulon 25w60 would be the way to go in the orange bottle. Dont go any thicker.

Really you need to sort out the leak, but you could give this a go first. They are only band aid fixes

 

[EVO-00X]

Old school V8 engines with big piston to bore or bearing clearances due to wear are a different kettle of fish. If they put in thinner synthetic oisl they'll blow it all out the rear end in less than a week and then cause more engine wear to lack of lubrication. Thick mineral oil is probably the acepted norm for those engines as thats the kind of oil that was around at the time of the engine being manufactured.
Rotaries have a problem with some brands of synthetic oils due to them not fully burning off carbon deposits.
When rebuilding our 4G63T's for high rpm and boost you'd be mad to use a mineral oil over a synthetic (except for say during the run-in period).

 

[milkandoj]

Yeah built motor are a bit different depending on the clearances they were built to.
I was referring to un-built motors in everything i said.

And with rotaries, that what i was getting at, the carbon deposits that arnt burning off with some synthetics, is because parts of the oil are so resistant to burning, the carbon deposites are the oil that isn't burning off.

 

[turbovr4]

semi synthetic is good to use but i found on a couple of my older motors when i tried to use mainly mobil 1 ,the motor used to drink the stuff.for example my old vr4 before i rebuilt it would use 1lt of oil to about 6000km of penrite hpr 15,but mobil 1 was about 1 litre to every 1000km.but as i said that was when i tried to use it in a 200,000km engine.I also think that was more from the turbo seals then.
Be carefull with thicker oils as they slow down the turbo spool.

but saying that with mobil 1 ,my fathers vr4 motor was fresher so mobil 1 wasnt being drunk as much as mine.
also too with the oils used i think it is how you drive it.i had mates that would use the best oil and additives change every 5000km not drive the car till operating temp and idle down every time they even drove without boosting,but drove hard in between.and we were still rebuilding ther motors and changeing turbos regularly.
I on the other hand just used pentrite hpr15,changed oil every 10,000km,drove sensibly on warmups,idle down for about 30 secs if onley using a little boost,drove hard but not insanely hard like they did.
anyway after 250,000km i pulled two of my motors apart and found good wear on bearings rings and bores only needed a lite hone,no lip,also running the same Td05 14b turbos.a little carbon on the block walls but nothing coked up.also still original lifters ,no rattle.
but hey,maybe im lucky.

At end of the day.just be sensible on how you drive the motor and a good quality oil without going overboard on price.

 

[OLDIE]

Rotary motors CAN use full synthetic IF you disconnect/shut off the factory oil feed that lubricates the seals AND ADD 2STROKE OIL TO THE FUEL TANK EVERY TIME YOU FILL UP as that lets you get the benefit of useing top grade oil and eliminates the possability of the oil metering pump failure. 2STROKE OILS ARE DESIGNED TO BE BURNT DURING COMBUSTION