Today's Motor Oil And Flat Tappet Cams

Joe in Oz said:
Someone mentioned the misuse of the term "clearance" and "tolerance" above.
Take note: they are VERY different animals.
Clearances are the gaps for the oil molecules to move in to prevent metal to metal contact.
Tolerance is the precision with which that clearance is produced and maintained.
In the 70s, those tolerances were such that most of the bearing width, for example, had the design clearances. The rest of the bearing width was either too tight (and would wear in) and too loose and servers no function in terms of bearing action.
Today, the clearances are maintained within millionth of inches across the entire bearing widths. No wearing in and full function of ALL of the bearing surfaces. In addition, the accuracy of surface roughness has improved out of sight.
That goes for pistons, bushes, mating surfaces etc. As a result, there is as good as no running in (wearing in) any more and engines last for 3 or 4 times as long as earlier ones with identical design clearances.
Oil development has kept pace with much less variation of molecule size and shape, reducing accidental metal metal contact for longer and longer periods.

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Now that IS interesting...and it rings true because of the short milage that we used to get in fords,chevy's and VW's and the like back in the 1970's
200k miles and it was well past a complete rebuild time....
Around here in the valley , it is nothing to have 100 degree temperature in the summertime..... in a cold climate obviously you need to run thinner oil because you actually want to start the car !!!!!! so Yah there are different scenarios that demand a different course of action.
in my location I have seen 125 degrees on the freeway in the valley.... next to the mountain here Now... I hardly ever see 100 degrees ! so it's quite a change for me.....much cooler here next to Mt.Shasta !
I still am thinking thicker oil is the way to go, but obviously not in every case
sense I am not in the super heat of the valley anymore putting straight 40w in my Honda CRV would probably not be the best plan !
but a multi grade of say 10-40w would be... when the engine warms up.... is when you need the thicker oil..... as oil heats up it thins out to a certain degree... so I will more than likely change the oil in my Honda CRV to valvoline 10-40w even though it recommends 5-30w
and because It is a multi grade oil I will change the oil every 5000 miles weather it looks like it needs it or not as the thickeners in the oil brake down fairly quickly....
5 years ago I would have said straight 40w for everything and it will last longer, but that was in the valley with extreme heat in the summer. and that strategy has served me very well over the last 2 decades .... but times change ....so must my thinking !
Bob.........
 
The design of engine dictates what oil to use. Valve spring tension is the factor in type of oil also.
 
Just wondering what the logic is to using higher viscosity oil in hot climates in a liquid cooled engine. Does the engine cooling system not keep up to demands? I remember pulling a trailer through the desert in midday with the AC on full but the engine never overheated.
 
Tozguy said:
Just wondering what the logic is to using higher viscosity oil in hot climates in a liquid cooled engine. Does the engine cooling system not keep up to demands? I remember pulling a trailer through the desert in midday with the AC on full but the engine never overheated.
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Higher ambient temps require thicker oil just like low temps require thinner, that's why we have multi-vis oil in the first place.

You may not have had trouble with overheating but I assure you many others have, even with a fully functioning cooling system on older vehicles. My Triumph TR4 would overheat just because when I lived in Arizona, and I had rebuilt the motor (including full hot tanking of block and head) as well as re-coring the radiator. I figure it was simply not designed for hot weather and would require modification of the cooling system to operate well outside of the mild UK climate.

That said, most manufacturers will have recommendations for operating under different conditions. I once had a plymouth station wagon where the owners manual told what you needed to do if running over 100 mph on a regular basis. And, yes it did:grin:

Cheers,

John
 
back in the late 1960's early 1070's I was coming into vehicle Age and I went after it with gusto !
being on the Ranch in northern california in an area that gets as hot as death valley Ca. Keeping the engines from boiling over when driven hard was indeed a constant battle .
although my first love was motorcycles I did own 3 cars in my senior year of highschool however none of them worked ! so I decided to get at least one of them running properly....it turned out to be a VW beetle, 36 hp,porthole rear window and beat to living death ! ignition was the main issue
and I found that first thing...no spark ! once running that engine would over heat just sitting there idling ! and I had no idea why....
finally I got disgusted and pulled the 4 bolts and dropped the engine out so I could work on the cooling system....
i drove that beast back and forth to the bust stop for the good part of 3 years and never had an issue with it being the bus stop was just a mile away.
..... you could tell when the engine was getting too hot as the tappits would really make a racket !
I drove it to town once a 20 mile one way trip and had to wait for the thing to cool down for fear of seizing the engine.turned around there and headed home... but didn't quite make it.... my Dad came by after work and towed me back to the house, I had seized the engine.....
....
....anyway when I finally got around to pulling the engine out, I discovered that the previous owner had bailing wired the air doors completely shut
and took off the thermostatically controlled actuating rams that opened them normally....
I finally found a set of those things and when I had the engine out I put them in .... I had seized only one piston to the cylinder wall.... I had popped the clutch and got it running again as Dad towed me home but I turned it back off to save the engine.....
I went to a wrecking yard and got a piston and cylinder from another 36hp VW and put it in and was eager to try it out....
but I was out of oil.... we had some 40w for the tractor...a 5 gallen bucket ..so I put the 40w in it when it called for 30w....
I fired it up and it never sounded that good before ! I thought wow it likes the 40w oil !
got in it and ran to town..... and it never got too hot... I was elated.... got home and Moms car had given up the ghost oh her in the drive way!
so I said take the VW......... I never got it back ! LOL...she loved that thing ! to me it was a car ...not REAL transportation ! I wanted a bigger motorcycle!... about a month later I got my wish with a Honda 305 Dream ! ..... but I never forgot how much different that engine sounded with that 40w oil in it ( and just tuned up) it didn't sound as Loose as it did before !
to make a long story short ( i know too late!) about 5 years later I had a New Ford Ranger off the show room floor, soon as it was out of warranty
I put in straight 40w oil ( valvoline)...... the same sound filled my ears from that truck as from the wore out VW.... I was amazed !
however when the temperature in Fernley NV. got down near Zero the Truck barely started... so I put 10w40 in it the next payday... and that problem was cured... come summer I put the straight 40w back in it..... the next winter the 10w40.... and so on....
I had the truck about 3 years when I enquired with the ford place as to how much I owed on it, and they said there must be some misunderstanding you leased this vehicle, I said no I didn't I bought it ! ( they fired the salesman shortly after I bought the truck)
so they got the truck back.... I wasn't about to rent a vehicle for love nor Money ! all those payments up in smoke ...I tell ya I was fit to be tied !
......
then My wife's folks gave us a car.... and we took it, as we were getting desperate ! a 68' pontiac bonneville brohm a "Tuna Boat !"
I put straight 40w in it first thing as it had 75k miles on it already and we drove it for decades ! till the folks gave us a brand new economy car ! a toyota tercel..... fantastic little car 32 MPG in a time when gas prices were at an all time high, and lines were forming as gas stations !
40w went in it after the warranty was off it called for 10w40.... we put 455,000 miles on that little car and one morning I noticed the Rods knocking
in it so I parked it...... it's still at the Ranch ! I was going to rebuild it but discovered the parts cost more than another car ! ( used of course)
so about then the wife's folks gave us another car, one they had been driving for ages a toyota Cilica ( it's out front with over 430k miles on it) and it's for sale, as they gave us their Honda CRV when they moved into the live in care facility ( old folks home)
......
.....so I WAS going to do the same thing and put 40w in it... but now I'm not.... I'll just do a thicker multigrade instead.....
if it weren't for my wife's folks we'ed be driving old beaters !
..... do you know if you disconnect the fuze to the radio in that CRV you have to take the car back to the dealer to get it to work again ????
that's my only complaint ! LOL.....( Honda's idea of theft prevention !...it's useless if you rip it out of a car!)
that's where I got my 40w is better idea from... practical experience.
Bob.........
 
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