10w-30. I use it in everything. Race cars and my 4 cyl Toyota PU, which tows a 5,000 trailer and has 308,000 miles on the clock.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Reduced economy, significant enough to measure. 2 to 3 percent is not "insignificant", especially with gas prices being what they are today.
That, sir, is a stupid thing to say. Taken a look at gas prices lately...? Economy matters whatever you drive, unless you're a millionnaire or own an oil company (same thing).
Yeah, it is. Thicker oil does not mean better engine protection. What's needed is film strength. Go spend some time over at www.bobistheoilguy.com to learn more than you ever wanted to know about engine oil.
Increased wear at startup...regardless of whether you nail the throttle or not. Thicker oil takes much longer to pump up and reach all the small clearances (e.g. between bearings and their journals, through small passages, etc.). Meanwhile, since you just cold-started your engine, it's running at about 1500 rpm on the fast-idle cam. That's certainly one way to solve the problem (wear the small clearances out so they're bigger, so the overly-thick oil you chose gets there faster) but it's certainly an expensive way to fix the problem.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

15W-40 Rotella T diesel oil. Has lots of additives that are good for our engines. These additives are slowly getting pulled out of regular oils due to emissions concerns.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Since I had my 93' suburban, which took 5w30 manufacturer suggested grade, I like to start at that point with other cars as well, If it doesn't foul the plugs and consume the oil you know your in good shape. My suburban had over 310,000 km and didn't eat it. My 85' slant shorty, however experienced a slight fouling in the #3 cylinder, so I moved up to 10w30 and have no problems not bad for 188,000 km.
Don't let a jiffy lube kid tell ya' that 5w30 is the same relative to temperature as 5w50.They tried it on me by mistake and I came back with the suburban and aguement ensued. That stuff feels like your oil pan is full of oatmeal once you hit the highway. Remember the most important thing is thinner is better for start up and highway economy especially( thicker can produce drag) and to thicker if you have high temperatures were you live but its hard to beat straight ol' 10w30.
5w30(because its thin) is great to see were you are mechanically when you first aquire a car and it cleans out and frees a lot of crud in your engine. My turned black immediatly and after changing up to 10w30 the next time following my engine/oil is clean as a whistle

My race engine expert, Paul Vanderely, recommends 50 wt oil in my hyper slant. It has 9.3 comp. ratio, Dual Dutra Duals and Eddy 4 bl on offy intake, larger valves and 272 degree cam with solid lifters and roller rockers. Paul has set the Bonneville speed record for 4 cyl. convert, well over 200 mph, and is still heavily into making race engines of all types. He is recommending the heavier oil for my car. I only have 170 miles on the engine, using it under light throttle because of torq. converter and transmission problems which I hope to rectify soon.

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Restored '62 Signet, 229 4bl, Offy intake, auto, Dual Dutra exhausts, shaved head and block, high stall converter, 1.6 roller rockers, etc.

Yikes. He's a fast racer and probably builds excellent engines, but his oil recommendation is...

...off. Way off. Unless your engine clearances are measured in fractions of an inch (instead of thousandths), 50 wt oil will do nothing for you but accelerate engine wear, reduce economy, and (if you rev it high and hard) eventually maybe shear off your oil pump drive pinion. 50 wt oil is best saved for squeezing a few more miles out of a thoroughly whipped, worn-out engine.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

FWIW I've been using Delo 400 15W-40 in all the 'old' engines such as the 318 in my van and my turbo brand X. The wife's Corolla gets 10W-30 though.

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Joshua

Ever since I was a kid in Alaska I have always used 10w-40. -20 F in Alaska, +115 F in Utah, +70 F in Washington, its all the same. I use 10W-40. ALthough, my engine buildr recommends straight 30 weight for the break in and first few thousand miles of life on his fresh motors. He's built two motors for me and both are doing well (one is the 225 in my brother's 83 Dodge van and the other is the Ford 351W in my 84 van).

I run 3:2 0W30 synthetic and 10W30 regular Valvoline in my "race" six. No problems. I want the thinnest safe oil possible in that application to glean more power.

D/W

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If it ain't broke, fix it!

I've heard of several people switching to the Delo from Rotella; some of the diesel guys claim that w/ Rotella, their engines are dropping wrist-pins around 100k miles.

Agreed on Delo vs. Rotella, which doesn't have a very good reputation amongst the regulars at www.bobistheoilguy.com .

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I changed from 20-50W to 10-40W this weekend. The motor seems to like it better. The only down side to the change, so far, is I have lost a lb of oil pressure. It went from #53 to #52. Idling or 65 MPH.

bwhitejr

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'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

That's not a down side at all. It means that the oil can move more easily through the engine so you are getting better oil flow. In the bargain you get better performance, economy, and engine life. Oil pressure is secondary to oil flow; as long as you are maintaining the factory specified pressure ( 45 - 65 psi @ 45-50 mph according to my '62 FSM ) you have adequate pressure.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

If you're using non-synthetic 10w40, be especially careful to pick a good brand. 10w40 is the grade that contains the most viscosity modifiers relative to the amount of actual oil. Viscosity modifiers (or "viscosity improvers") are what is added to a thin base oil to enable it to behave like a thicker oil when hot. Logic says that the same amount of viscosity-modifying polymers would be required to create the 30-point spread between 10w and 40 as between 20w and 50, but apparently this is not the case for reasons I don't fully understand. The high level of viscosity modifiers is why 10w40 has a reputation for being one of the more sludge-prone oil grades. 10w30, 15w40 and 20w50 are less sludge-prone because they don't contain as much of these polymers.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

just to clarify, since I have heard a dozen suggestions on this thread, what oil, and for how long, do you use for a fresh rebuild?

-dave

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what part of "illegal" is so confusing???