I just got back from a 700 mile club trip and almost had a bad experience. Due to my own fault, I forgot to check my oil for quite a distance (get gas, in commotion forget to check a few times). Yesterday day morning I noticed a 20psi drop in pressure and checked my oil very quickly. I found I was 2.5 quarts low, and got a very uneasy feeling. Other engine savvy folks in the club said that they felt it would be fine as the pressure was still there and there was oil evident at the valves. My bigger issue is that all who followed said they saw no evidence of oil burning in my exhaust and the car runs perfect. The folks with older Vettes said that they watch their oil closely and typically have to add at regular intervals due to old engine tolerances. They calim the enginees run hot and "eat it". They too show no evidence of oil burning. By research this morning, it appears that I should make a move to 20w50 oil, and possibly even to a Castrol classica car oil (mine is a '78). Presently I was using a 10w30 which appears may be too thin for the "sloppier" engines of the 70s. I am looking for some input, as the thought of a valve job and long term engine wear concerns me. FYI-the engine shows 36,000 on the clock.

 

If you're going through a lot of oil and aren't ready to rebuild, I would recommend that you use a 10 - 40 name brand that you can find anywhere. Then you can keep it full without carrying a five gallon bucket of your specific brand and weight with ya.

That's my .02

 

How many miles between oil checks? 2.5 Qts in 700 mi is a Lot! Even in a high performance situation I would expect you might be down a quart. Have you done a compression check? How many miles on this engine? I have only run 20-50 in old 4 cyl engines.

 

That's just when I forgot to check on this trip. I put on about another 600 on a previous trip, and had just changed the oil before that so didn't chekc druing that trip, I don't believe. All and all It has probably been 1500 miles or so. I am not opposed to a valve job, but I first want to explore the first and foremost. Almost all major oil company web sited reccomend 20w50 for older engines, as the additives in the new oils have cahnged and some of the properties of the oil which are great fro today's engines allow don't work as well for yesterday's engines. Castrol even now has "classic: car oil, of which one type is for pre-80s cars.........The data claims that there used to be components in the oil to help seals and gaskets of the day swell properly. Because of the different materials used in seals and gaskets today the gaskets, seals don;t swell properly. These calssic formulas provide the proper chemicals to provide for theis. The 20W50 is reccomended because the thicker viscosity of today's oils work better with the sloppier tolerances and large passages of yesterdays engines. I figured I would start with basics, and if that didn't help, a vavle job would be on this winter's to-do list.

 

2.5 quarts even at 1500 miles is alot. i would be concerned at anything approaching 1qt per 1000 miles. i don't think the 10w-30 is the best selection for you either, you can start at 10w-40 and if that doesn't reduce your consumption, then definately try the 20w-50. that is what i'm currently running but i have 160k+ on this engine and drive it hard.
BTW, i don't want to tell you how i know this but a SBC can run at >2 quarts of oil without damage. as long as your not tearing up the streets.

 

I use 20w-50 All Year Round. I have 91K on my '78. I don't start it under 40*. I have 3:70's and I'm running around 3500-4500 rpm's. So between the age and rpm's I don't want to use a lighter oil.

 

Some of club mechanical experts said as long as the presuure is up you're fine. I was still at 30psi. You're still pumping enough oil to do the job. the only reason I am going to 20w50 is because the Castrol, Pennzoil, and Valvoline websites claim this is what you should use on older cars (pre 80) beacuse of engine sloppiness. Today's oils are designed for very tight tolerance engines and thus the additive put in these is different from years ago, even thought the SJ oils meet or exceed pre-80 levels. The Castrol classic products are designed to emulate oils of years ago. Some of the articles even talked to oil being "eaten up" because of these newer additives and thiness of viscosity. I think my approach is going to use 20w50, moniter the consumption very closely, and if consumption is still high, investigate the cause. I hate leaking or "lost" fluids....it will drive me nuts.

 

I think you are getting a lot of marketing hype there. The only way I would ever use a 20w50 weight oil is if I had a worn out engine and needed the thicker oil to fill the gaps in the bearings. In my '73 454 I run 5w30 or 10w30 Mobil 1. Never anything heaver.

The only reason for "engine sloppiness" in per '80 cars, or any car, is a worn engine. If the engine is worn out, all bets are off. If the engine is good there is no need for any special oil. Just run a name brand 10w30 and a good engine will be okay.

In your case, I would keep using my current oil and monitor the oil very closely to determine for sure how much it is using. Could be it is time for a rebuild. But may not be. But first you need to positively determine the oil usage.

tom...

 

Be very carefull with using something as thick as 20W-50. I used it a few years back and it took so long for the thick oil to get to rocker arm #1 that the pushrod, rocker and rocker ball got eaten up and had to be replaced.

I don't agree that older engines are loose and should use thick oil. Mine was rebuilt 40k miles ago and uses 1 quart in 2500 miles. this was with a fairly major leak coming out the distributor (where it goes into the intake). I've since fixed that so consumption will decrease further. I use 10W-30 mobil 1.

 

On my 460 with a new rebuild, and .002 main bearing clearance. I started it up and continue to run 20W50. for 60,000 miles now...
I tow heavy and out here I tow in 120 degree air temps, Don't tell me that 20W50 is not good for newer motors.

The reason for the rebuild was running what ford recommended in the first place (10W30), spun the #7 & 8 bearings... towing in 100 degrees at 59,000 miles.

Now it's 20W50 pure synthetic forever. and yes I run it in my vette also with 106,000 miles.

 

The owners manual for my 75 lists the following:

For temperatures below 20 degrees F: 5W-20, 5W-30 but with a warning that the 5W-20 is not recommended for sustained high-speed driving, while 5W-30 IS recommended for Canadian vehicles.

For temperatures between 0 and 60 degrees F: 10W, 5W-30, 10W-30, 10W-40

For temperatures above 20 degrees F: 20W-20, 10W-30, 10W-40, 20W-40, 20W-50

It also says that a straight 30 can be used for temps above 40 degrees. With these in mind you will have to determine what works best for your air temperatures and driving habits. I live in Sacramento California where the summer lows can drop way down in the low 50's so I run a 20W-50...if there was a 30W-50 available I'd probably get some of that for the summer, but I run 20W-50 all year round...it never drops below 20 F (lowest I think I've seen is 26 but only for like 4 hours then hopped back up to 28) so for me a 20W is fine with the specs.

Illinois may get into the teens depending on where you are, so you may want to change your oil at the start of each season. Right now you could use some 20W-50, but around October or November you might want to change it out with some 10W-40, unless you aren't going to drive it any during the winter.

I've never heard of Castrol Classica...just check and make sure it's Dino oil and not all synthetic. The synthetic has better lubricating properties, but it's not as good at staying in the bearings and cushioning the impact like dino oil. I use off-the-shelf Penzoil for street driving, but I switch to Penzoil Racing Oil for the track. The racing oil will get dirty after just a few hundred miles of driving.

 

One thing to not forget, that recommendation is now 28 years old and was based on the oil available at that time.

tom...

 

See bobistheoilguy.com for good discussions on oil and filters.

 

Thanks for the advice...all good. The last statement kind of hit what the oil manufacturers are saying, that the oil of the 80s and earlier contained different additives than today, most of which allowed the seals to swell more (due to the seals being of differnt lower tech materials). The "Classic Castrol" products supposedly use additives the same as the era. I found some seperate articles (not from the comapnies) which talk to using 20w50 in pre-80s cars due to wider tolerances and bigger oil passages. the funny thing about my car is that it was real good all last year, very little usage. I put in I believe 10w30 and went on (2) long distance trips, and this appears when the consumption started. So either something in the engine has given way somehow, or it was the oil viscosity change. My apporach was going to be (as stated above) to tyr the 20w50 and moniter usage very closely and log it. If it is excessive I may have it chekced out in the fall. What's really odd is for that kind of consumption I would expect blue smoke, but there is none. No oil on the floor, no evidence of leakage anywhere. I am just wondering if my lack of monitering over numerous trips in very hot conditions is where it dropped, I just didn't find it until now. I have definetly learned a lot about oil viscosities through all of this. I hope I don' have to go through the rebuild............

 

With driving around town, I 'consume'/burn/leak about .5 quart every 500 miles. Spark plugs are clean and very little signs of leak on underside of engine/trans pans. I suspect I have some clearance issues that allow 'drips' of oil to get into the combusion chamber. Again, no fouled plugs and no noticable smoke.

BTW, I use Store brand 20W-50 and change about every 2500-3000 miles.

 

Believe your oil consumption is due to valve guide seals that have become brittle over time, and due to this brittle condition are no longer effective in preventing this type of oil consumption. Solution is to replace them, which can be done with the heads on the engine, no need to remove them, and no need for a 'valve job', as you indicated you might need.

All in all, this job can be done by amature mechanics like us in a day with the right tools, and can be done for under $100 for necessary valve guide seals, and new set of valve cover gaskets.

Personally, I wouldn't run anything thicker than 20W40 in an engine with only 36,000 miles.

just my thoughts...........

 

I've heard about oil consumption in other threads. But, I just changed my oil...fresh 20W-50 and an STP oil filter (never will buy a Fram again). My oil level was nearly where it was last September when I changed it last. My engine has almost 50K on it, and I do smell something like oil burning...but have not seen any drop in my oil level. Could it be because I've been using 20W-50?

 

Asking about oil around here is like asking about religion or politics. Everyone has their own opinion!!! I run 10w30 in winter and straight 30 in summer. Despite having bad valve seals, I do not have a serious consumption problem.

Oil viscosities have not changed. They are based on an SAE standard scale. Additives and viscosity improvers, on the other hand, have changed greatly.

But none of that matters in your case. You have an oil consumption problem, pure and simple. Most likely culprit is valve seals. Does your engine blow a blue cloud of smoke when restarting an hour or two after a long run? That's a telltale sign of bad valve seals. It's not a critical issue -- as long as you keep your oil level up -- but it sure is annoying!

 

:confused: I thought that was the factory smoke screen option, very rare! (At least that's what it says on e-bay.)

:jester

 

Every now and then I do get the intial puff on cold start; engine warm nothing. I had the same issue on a Blazer a number of years ago and it was bad seals. I have never repalced the seals myself but have most definitely have removed the covers and adjusted valves on various automobiles. I will consult my shop manual to see what it takes. If it is that straight forward, I will attempt it. This kind of stuff drives me goofy. I have other club members who are telling me, its an older engine, wathc the level, if its burning clean and runs good just maintain your oil levels. I hate saying I have an engine that uses oil...just bugs me. I guess I might be a bit ****. :cry :cry