[lslapshot]

Hello everyone. I have a 67 GTO with a 400 auto. and was wondering what oil viscosity is recommended? I followed the instructions from the previous owner and used Amsoil SAE 30 and now the car sounds like someone is tap dancing under the hood. I think I need something thicker? not sure what to do. Any help would be appreciated...Lou

[lslapshot]

Hello everyone. I have a 67 GTO with a 400 auto. and was wondering what oil viscosity is recommended? I followed the instructions from the previous owner and used Amsoil SAE 30 and now the car sounds like someone is tap dancing under the hood. I think I need something thicker? not sure what to do. Any help would be appreciated...Lou

[gtoformula]

I run 15W-50 Mobil 1. The low cold viscosity helps with cold operation and the 50 wt is good high temp insurance. The car doesn't get driven much so synthetic helps with start up oiling as it sticks to moving parts better than mother nature oil. It also doesn't need to changed as soon. Time and mileage are difficult to calculate for these older, infrequently driven cars.

[gtoformula]

You really can't go wrong by trying different oils ... just don't mix them or you won't realize the difference.
Yeh, Mobil 1 is $4.25/quart, but you don't have to change it as often, it protects better at start up and may reduce your engine noise.
Gotta ask yourself, "Why not buy the best for my toy?". Especially when it's worth so much. How many modern cars are appreciating assets?

[78 GHOST]

I run Castrol 20-50W in everything. I ran Mobil 1 in the T/A for one oil change.. the engine had around 70K on it and right after I switched it developed a bit of valvetrain noise.

As I was commuting from Cincinnati to Cleveland at the time, I stopped by and spoke with the Kaufmans about this. Mark was very helpful and pointed out that synthetics are super detergent in nature. Basically, they tend to loosen up deposits on older engines, and these deposits can dislodge, migrate, and become stuck in places you really don't want them in such as lifter bodies.. hence the noise.

His recommendation was to revert to ordinary fossil oil and hope the problem goes away. I did and the car quieted right down.

I believe that it's best to break in a new engine on fossil oil, then use synthetic from then on. On an old engine you might be tempting fate.

[wheelspin]

Pitts,

With that mileage I would recommend 15-50 Mobil 1 for the additional bearing clearance.

Les

[prostreetpower]

i use 20-50 pensoil on my 77 trans am and it runs great. Any 1 have any experience with royal purple? Was thinking of trying it out next oil change, always advertised on the SPIKE channel ( Horsepower Tv, trucks, etc. ). THanks for any info on it guys

[WallyB]

You need a blend for typical use. The first number should be a 5W or 10W (weight) The 5W for winter starts, below 40F & the 10W for summer. The second number should be a 30W or 40W. So a 5W-30 for winter use is good, 10W-30 for moderate temperatures and average use, go to a 10W-40 for harder use (long highway runs or towing) These are typical suggestions. When you get into the 20W-50 oils, they are really thick and can damage your engine over time, mainly from the start up in cooler weather. Some people use 20W-50 to help worn piston ring problems and push the life a bit further before the engine gets tossed or rebuilt. Carburated cars usually won't start at cold temperatures without a couple of throttle pumps, so before you pump crank the engine for 10 seconds or so a couple of times, this will pump the oil up to the valve train and lube it before starting. Then pump it & start. Synthetics should only be run in late model engines or new rebuilds that can handle them - can't be mixed with conventional fosil types. Stick with a brand that works, frequent oil changes with a new filter. I'm not a mechanic, but these suggestions came from good mechanics, common sense guidelines.

[Junkyard Dog]

I wouldn't use 5W-30 in that engine. The base stock is a 5 weight! USe 10W-30 Valvoline and call it a day.

[Z Code 400]

I have found that film strength is often overlooked with engine oils. Oil pressure is lower with thinner oils.

I run nothing but 20/50 ever. However, it was also 106 degrees here yesterday and it hardly ever reaches 32 degrees in the winter.

I tend to break an engine in on straight 30 or 40 weight Valvoline Racing Oil. The only reason for using the 'racing' formula is the added zinc, (which makes it unlawful for street use in Kalifornia since zinc destroys cat convertes), has better EP properties.

The added zinc is a no-no from an EPA stadpoint, hence the 'racing' moniker which identifies its intended 'off road' use.

I change oil and filter after the first 30 minutes of running. I then change oil and filter every 100 miles for the first 500. After that, I change oil and filter every 2000 to 3000 miles on a carbureted vehicle and every 6000 to 8000 miles on EFI cars.

I have always done this and I believe the most important benefit is removing the maximum amount of foreign material from the engine as rapidly as possible.

I am not suggesting you adopt my method as I am sure many people will have something negative to say about the technique, but it works for me.

If you like synthetics, that's fine too. The new BMW V8's require a special oil made by Castrol that is a full synthetic with a 15/65 viscosity.

Available at all BMW dealers for around $4.00/quart.

BMW found out the hard way with their 'M' Series cars that regardless of the additives, low film strength will kill an engine. That's straight from BMW.

My neighbor used to run 5/30 Mobil 1 in his BBC and he kept having a problem with rod bearings. He never did 'spin' a bearing, but he picked up a slight 'knock' and they looked like hell when he pulled them out.

I asked him about oil pressure. He had about 15 to 20 psi hot at idle and about 40 to 45 at 3000. I told him I thought the oil was simply too thin, especially for 6500 to 7000 rpm.

This cycle went on for a while and ultimately, he asked me to help him correct the problem. I checked clearances and found everything to be good. Rods and main registers were also right on size.

I installed a factory GM high pressure relief spring (once known as the off-road spring) into his stock pump, polished the main cap entry into the cap and block and used 20/50 Valvoline.

Oil pressure is now 40 psi at idle hot and 60 at 3000 hot. The engine has been together now for 3-1/2 years, raced weekly and driven daily.

Thin oil anyone??? Not for me. If you are having good results, that's great. To each their own...Robert

[Lloyd-TX]

Robert, you bring up some valid points.

My experience with running Mobil 1 5W30 in the newly-buit 455HO in my blue Formula has been great. About 2000 miles on it now, and the oil pressure has remained consistent since it was first fired on the dyno. Generally 65-70 PSI at cold idle, 35-40 PSI at a 800 RPM hot idle, and 65-70 PSI hot at 3000 RPM and above. Dunno what any of my bearings look like, 'cause thank goodness I haven't needed to look at them, LOL!

[Z Code 400]

That's actually very good and consistent pressure from such a thin fluid medium. As previously stated, if it works for you, stick with it.

Personally, I use the heaviest oil I can find and I would prefer 30 w 60 if I could find it, since that would cover our climate perfectly.

Lloyd, did you break that 455 in on Mobil 1????...Robert

[Lloyd-TX]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Robert Herndon:
That's actually very good and consistent pressure from such a thin fluid medium. As previously stated, if it works for you, stick with it.

Personally, I use the heaviest oil I can find and I would prefer 30 w 60 if I could find it, since that would cover our climate perfectly.

Lloyd, did you break that 455 in on Mobil 1????...Robert <HR></BLOCKQUOTE>

A few more points to consider, Robert:

1) Even in our very warm climate (CA and TX), a 20W40 or 20W50 oil is S-L-O-W to flow to critical engine components upon a cold engine start. It's been well documented that 95% or more of engine wear occurs during the first few seconds of a cold start.

2) My engine builder recommended 5W30 Mobil 1 engine oil to me and he set the bearing clearances accordingly. I am running the RA IV style (60 PSI relief pressure) Melling pump, BTW.

3) Yep, from the first moment it was fired on the engine dyno 'til today, nothing but Mobil 1.

Talk later!

[Dryseals]

Just a few things to think about. The pump system in you car sucks up oil and pushes it through the block. Your oil pressure gauge is normally on the back end nearest the pump. It still has a long way to go before it reaches all the bearings. Using a higher V oil will increase the pressure at the gauge not because of more flow, but because of more resisance to flow. By the time it gets to the bearings it encounters a small clearance and then slings out. The higher the V, the harder it is to push that oil into the bearing causing more back pressure.
Its has always been my opinion, that if you go with a higher V than required by the manufacturer, then you need to increase the flow with a non standard pump.
The multi viscosity oil functions as easier flow when cold, lower number, and harder to flow, higher number. If you see higher temperatures then your flow will be decreasing with a larger number.
Pressure at the gauge is not an indication of flow, just an indication of back pressure.

[Z Code 400]

I tend to stick with those things that have proven themselves to work for me over the years. This is one reason with 20/50 oils.

If you want to consider the manufacturers recommendation, we could look at the 1979 Trans Am Owners Manual which recommends a 20/50 in my climate and cautions against using low viscosity oils for sustained high speed driving.

Or, if film strength is indeed meaningless, then BMW must be foolish to have Castrol market a 15w60 oil for their new V8 engines.

If I lived in Alaska, I might use a thinner oil, but where I live, I do not consider a 5w30 or even a 10w40 as being a sufficient lubricant in my engines.

With my enlarged and polished oil passages, my engines develop higher, more consistent pressure than most other engines I have seen.

When I say 'consistent', I mean 50 psi @ idle hot and 65 psi @ 3000 rpm is the norm.

When I was racing the 429 Ford and spinning upwards of 7000, we ran well over 125 psi cold oil pressure and around 85-90 psi hot at 5000 rpm.

This pressure was needed to keep the bottom end alive with their large bearings and high rotational speed.

Don't believe it??? Moroso still offers the Ford NASCAR 100 psi spring and if you have the right part number, your local Ford dealer still carries the Motorcraft version.

I recently built a 350 Vortec for a friend and polished the oil passages and blended the cavity in the rear main bearing cap; a huge source of restriction on an engine.

Into this basically stock small block Chevrolet, I installed the Big Block Oil Pump with the GM #3848911 "Off-Road" relief spring.

His oil pressure (with 20w50 oil) is 50 psi @ idle hot and 60 psi @ 3000 rpm, which I feel is optimum.

Oils and pressure are very subjective and everyone should run what they want to. I'll continue to use what has proven itself in my engines.

In case you are interested, here is a shot of the oil passage (pump entry to block) on my 1970 Pontiac 400. Every passage in the engine, including the filter housing and oil pump body is enlarged and polished.

The lifter galleys are drilled (3 foot long bit) and then reamed to final size. This eliminates the 'uneven' bulkheads you often see when looking down into the passage.

I've tried every kind of oil you can think of including Royal Purple (used to be marketed in the 1950s as Royal Triton and it was purple then too) Amsoil, RedLine and Mobil.

I've never had the consistency in oil pressure with a thin oil. I just don't use them, so there is more for you guys... ...Robert

[Z Code 400]

And, just in case you are interested, here is the same passage in my stock 1979 400 block.

And by the way, I guess I am very anal about this kind of stuff, in case you didn't notice...Robert

[fastgto]

20/50 here

[BAB]

Robert,

Very nice..! What did you use after the three foot drill bit (to ream)?

[Z Code 400]

Bab,

My Dad had a bunch of reamers. All kinds...most of them were for toolmaking. I found one that was adjustable and had a pilot. It was also about 3 feet in length.

When you looked down my oil galleys, you could tell my black had suffered some casting shift, since the passage was not straight.

I drilled the passage until it was straight and used the reamer to 'clean' up the surface.

I then asked my Dad to make an arbor for the cartridge roll that is about 3 feet long, so I was able to polish every passage to a mirror finish.

I also have flush-fit taper-back 3/8" pipe plugs from a 429 Ford in place of the front oil gally 'knock in' plugs.

Dad's been doing this to Flathead Fords for 40 years and I grew up around those engines. I just apply the same technique to this 413.

It's probably not necessary, but I like the way it works and looks. Much better oil pressure with less than 15 PSI change between idle and 3000 rpm.

Most passages are shaped and polished with a cartridge roll in a 3/8" electric drill.

E-mail me at [email protected] if you need more information...Robert

[buwalda]

Here in Australia, we have an oil company called Penrite, that makes engine oil for our hot climate, including 40w/70 for worn engines.