What oil should I use?

obxfshn

obxfshn

Daily Driver
I’m in the process of changing the oil in my 1500cc FI 1981 X. I bought mobil 1 5w30 full synthetic and a quart of Lucas synthetic oil stabilizer. I’ve used Lucas in the past with oil engines (sunk a 4 wheeler in a pond and the engine filled with water; oil was milky white and after a drain and clean it ran great).

A local mechanic warned me that synthetic can damage an older engine.

What is your advice on synthetic vs regular oil? I’m about to drive this car to the blue ridge mtns and do a lot of mtn road driving and don’t want to screw up the motor!

Thanks for your advice!
Brandon
 
Pretty much like spark plugs - gonna get a full range of responses.

I would not use synthetic in an engine with original vintage oil seals. My speed shop/machinist suggested not using any synthetic in an older motor. I switched to Valvoline VR1 20W50, becuase it appears the zinc additive is necessary in my case.
 
Did the mechanic say how synthetic oil could damage an older engine? From my first car in 1965 I used to run 10/30 Valvoline in my cars. Older with 90k I would use 20/50. For the past ten years or so I have been using Royal purple synthetic in my cars. No problems so far.
 
dragonsgate said:
Did the mechanic say how synthetic oil could damage an older engine? From my first car in 1965 I used to run 10/30 Valvoline in my cars. Older with 90k I would use 20/50. For the past ten years or so I have been using Royal purple synthetic in my cars. No problems so far.
Click to expand...

I don't remember exactly, now. May have been not worth the additional cost. Mainly the concern was the zinc, given the cam & shim wear I experienced (that was not oil pressure/bearing wear related).
 
Oh my, I really laughed when I saw the title of this discussion. I know your question is sincere Brandon, but history tells us this is one of those highly volatile topics. Can't wait to see where this one goes...(we need one of those emoticons of a guy eating popcorn).

Just to be clear, I'm not laughing at Brandon for asking. It just reminds me of so many heated debates backed by so much folklore, internet "facts", and personal opinion that never seems to end.

That being said, I will contribute my fuel to the fire. Regarding zinc in oil, several years back it was popular to use a Shell oil (Rotrella for diesel engines) for engines needing zinc to protect the cam/lifters. It was readily available, affordable, and had the highest levels of zinc for a regular production oil. However at some point Shell removed the zinc due to EPA(?) regulations (or something like that), but it was not publicized they had done so. About the same time several "specialized" oils came on the market to fulfill the demand of the 'muscle car' crowd. These tended to be very high priced and not readily available at your local stores. I see the Valvoline oil Huss mentions (VR1) contains zinc and is offered in both regular and synthetic versions:
https://www.valvoline.com/our-products/motor-oil/racing-synthetic-motor-oil
https://www.valvoline.com/our-products/motor-oil/vr1-racing-oil
Huss, how available is it and at what kind of price (compared to other oil products?
 
Last edited:
I was under the impression some Rotella still contained zinc levels friendly to our engines. Perhaps I was wrong.
 
This has been talked about before. The X1/9 is a flat tappet engine so modern oils, no matter what brand, will not properly protect this engine that was designed in the 1960's. The consensus from the experts, including Bernice from this forum, is the Shell Rotella 15-40. I have always thought that this was because of the high use of ZDDP, which was gradually reduced in motor oils over the years. One expert's opinion (I don't know his name, just copied his opinion, as well as others into Word files) is that higher ZDDP in the diesel 15W-40 is the reason why the cams last longer. But, people freaked out when the ZDDP was reduced in the Rotella to make it safer for the Cat and O2 sensor. The real difference is the HTHS (High Temperature High Shear). Again quoting an oil expert's opinion, "SAE xx rates oil viscosity at 100C/212F and HTHS rates oil viscosity and shear at 150C/302F." From Lubrizol Additives 360: "High temperature high shear (HTHS) viscosity of engine oils is a critical property that relates to the fuel economy and durability of a running engine. The drivers behind lowering HTHS viscosity are new global governmental regulations to improve fuel economy (FE) and lower greenhouse gases (GHG) in new vehicles. Lower HTHS viscosity tends to improve FE and lower GHG but higher HTHS viscosity affords better wear protection so a careful balance must be found when formulating an engine oil. Sufficient HTHS viscosity is critical in preventing engine wear in the critical ring/liner interface area by maintaining a protective oil film between moving parts. Think of the protective oil film as if you are trying to swim. If the film is too thick like molasses you can barely move and have to expend a lot of energy; too thin and you sink to the bottom. What you want is the right balance of support and ease of movement. The oil has to be thick enough to maintain separation of the critical moving parts but thin enough to allow for fuel efficient operation."

All SAE 0W-30,5W-30,10W-30,0W-40,5W-40 and 10W-40 ratings have the exact same minimum HTHS requirements. (2.9 at 150C/302F). So, a 10W-40 is NOT necessarily any thicker at 150C than a 0W-30. An SAE 0W-30 that is also ACEA A3/B3, A3/B4 or C3 approved has a minimum HTHS requirement of 3.5 at 150C/302F. So an ACEA A3/B4 approved SAE 0W-30 is actually required to be much thicker at 150C/302F and provide far better HTHS shear protection than an SAE 10W-40 that is not ACEA A3/B4 approved is required to provide. YES, a 0W-30 can be thicker than a 10W-40! SAE 15W-40 has special requirements that exceed the individual "15W" and "40". They include a minimum HTHS of 3.7 at 150C/302F. I know this sounds complicated as it did to me. I'm not an oil engineer.

Typical SAE 10W-40 and SAE 20W-50 products are discouraged by virtually every OEM and they are not approved by any OEM for use in modern cars. So, many oil companies that make them use their cheapest base stocks in these products and the result is inferior protection when compared to other modern oil products. These 10W-40 and 20W-50 products do NOT share the ZDDP limits that the more common ILSAC (International Lubricant Standardization and Approval Committee) approved 5W-30 and 5W-20 products have, but the absence of those strict ZDDP limits in 10W-40 and 20W-50 has not shown any real advantage in camshaft protection.

The ACEA A3/B3, A3/B4 or C3 ratings will insure that the oil provides good protection under HTHS conditions. You can find these ratings in the Castrol Edge 0W-30, Mobil 1 0W-40, and other similar products. These products will be thin enough to allow the flow required to flush away abrasives and will still provide the required high temperature high sheer protection. You will NOT find that approval in Mobil 1 5W-30, Mobil 1 10W-30, Mobil 1 0W-30, Castrol Edge 5W-30, or other similar products. These are NOT the correct oil products for flat tappet lifters, such as our X1/9. So, just using ANY Mobil 1, Castrol Edge, Royal Purple, or what ever brand you are trusting, is not the answer. Only certain products within those lines (and others) meet the requirements.

Besides the Rotella, these are some other oils that are recommended for our engines.


AMSOIL SYSTHETIC ZROD 10W30 (ZRT) (ZRP)

LUCAS ROAD AND CLASSSIC HI-PEFORMANCE

ROYAL PURPLE HPS HIGH PERFORMANCE STREET OIL

VALVOLINE VR1 20W50 10W30

I would like to hear other people's opinions.
 
So Ron, are you saying that our old standby, Castrol GTX 20-50 (or 10-40) should not be used in our Xs and spiders?
I have been using GTX in my Fiats since last century. Also, what is the failure mode on the tappets and cams so we will know if things are getting ugly?
 
Dr. Jeff is correct in saying this topic surfaces every so often and everyone has an opinion. I do not preach, just state my experience. Back in 1972, a buddy of mine who raced 850's told me to use nothing but SAE30 oil in my Fiats. After many, many years and five Fiats later, I still use 30 weight. My current car has 135,000 miles on its original crank and pistons. BTW, its getting more difficult to find 30w, and sometimes the clerk asks me if I use it for my lawnmower!!
 
lookforjoe said:
I bought cases (six quarts per) from Carquest - I think it was about 36bucks a case, so around $6 a quart.
Click to expand...
I'm not sure which Valvoline VR1 you have, the regular or synthetic version. Which one is that price for? Thanks.

Fiataccompli said:
I was under the impression some Rotella still contained zinc levels friendly to our engines
Click to expand...
Chris, it is my understanding that they changed the formula and it no longer has the high zinc (ZDDP) content. According to what Ron posted, that may not matter though?
 
carl said:
So Ron, are you saying that our old standby, Castrol GTX 20-50 (or 10-40) should not be used in our Xs and spiders?
I have been using GTX in my Fiats since last century. Also, what is the failure mode on the tappets and cams so we will know if things are getting ugly?
Click to expand...
Motor oil produced in the 60's to the 90's had a decent amount of ZDDP in them to protect flat tappet engines. When it was gradually phased out we had to look for alternatives. I used to use Castrol GTX and Valvoline 20W-50 Racing oil in my race engine back in the 80's and early 90's.

When the tappets become worn the tappet base becomes concave (dished), so that when the camshaft rotates through 360 degrees the tappet will only ride on the edges of the camshaft and only make contact in the center when it goes over the worn cam lobe. This has the effect of causing the camshaft to be brown in appearance and shiny on the edges. What I don't know is how long it takes for the wear to show on the cam.
 
Joe F said:
Dr. Jeff is correct in saying this topic surfaces every so often and everyone has an opinion. I do not preach, just state my experience. Back in 1972, a buddy of mine who raced 850's told me to use nothing but SAE30 oil in my Fiats. After many, many years and five Fiats later, I still use 30 weight. My current car has 135,000 miles on its original crank and pistons. BTW, its getting more difficult to find 30w, and sometimes the clerk asks me if I use it for my lawnmower!!
Click to expand...
Many of us (me included) tend to believe friends or people "in the know" when it comes to engine oil. For a long time I avoided using Quaker State because a racing friend of mine had a camshaft wear out in his Corvette in less than 30,000 miles and he regularly changed his oil with Quaker State. I found out some time later that GM had a problem with their camshafts in the Corvette. It wasn't the oil's fault.

Using straight weight oil seems ancient with the advent and regular use of multi-weight oils now, but the 30W oil might still be Ok for the old 850 engine, but not for more modern cars. Back in the 60's my dad raced on oval tracks. Everyone was using STP oil treatment. Today I can't believe people poured that thick stuff into their crankcases. Who knows what oil will be like in 20 or 30 years, or if we will still be driving internal combustion engines.
 
Very good and technical information! Thanks all who commented. For this change I used what I had on hand in my original post.

For the transmission change I’ll use Redline 70w80 MTL.

These were the fluids that the PO had used.

Thanks again everyone!
 
In Australia where we don't get the extreme cold temps as some parts of the US I have always used 20W-50 grade oil in all my Fiats from the 1970's following Haynes workshop manual recommendations (it keeps good hot oil pressure at idle and also good for light track work). Since synthetic oil prices have dropped I have switched to them for both my X's with the advantage of being able to get 5W to 15W -50 grade for better flow at start up, no problems with oil leaks or anything. Currently using an Aussie oil Penrite with high zinc content, but Mobil 1 do a 15W-50 oil recommended for flat tappet applications with fairly high zinc and HT/HS. https://mobiloil.com/~/media/amer/us/pvl/files/pdfs/mobil-1-oil-product-specs-guide.pdf
 
You must log in or register to reply here.
Back
Top