which engine oil viscosity?

[outdoorman]

The family has 4 automobiles-Ford Bronco, crown victoria, toyota sienna and saturn SL2; not to mention  Son's 4 stroke dirtbikes.  Upto now, I have 3 diff viscosities of motor oil- 5w30, 10w40,5w20 between the cars.  My question is how important is it to stay with the manufacture recommended viscosity? I live in Georgia where the temps rarely get below freezing but does get up in the high 90s during the hot summers. Would it do any damage to engine to go with 10w40 in all the cars?( its kind of a hastle to buy and keep all those diff viscosities)

[1sourdough]

  For the most part yes I think you would be fine. I do it myself with some vehicles. Even though it may say something on the oil fill cap the book may show several oil options. I think a lot of the 5w-30 craze is mostly for gas mileage. The manual also takes logical think out, just compare a ND Winter to that of FL. The manual would still call for the same oil with those extremes. I'm trying something new this Winter. That would be full synthetic in at least one of the vehicles.  At times I have used an engine heater for an outside vehicle & may just skip that & try this synthetic for that cold temp crank. I don't believe the difference from 5w-30 to 10w-40 would matter, especially in a moderate GA climate. Of course some would say  you should never deviate from the book.

[Lloyd Smale]

for the most part newer engines are built with much tighter tolarances then they were 15 years ago. Its one of the reasons that anymore its easy to get 200k out of one. That and oil formulations have improved over the years. In a gas motor anything heavier then 10/30 just isnt needed and in some cases will restrict flow accross your bearings. I run 5/30 in about everything and if i lived down south id probably use 10/30. But unless your running a diesel anything heavier isnt going to help and thing and may be worse. cold start is the worse thing on your motor and getting oil to your bearings then is the most important thing and in cooler temps thinner oil just flows much better.

[SHOOTALL]

We run up to 40 trucks ( PU . Vans and stake body )and use 10-30 syn. for everything. Some call for different oils ( thinner) but we experinced longer eng life with 10-30 syn. over other oils. We used amsoil for years but have switched to NAPA syn which is Vavoline syn. We have seen no more problems but have seen reduced cost. We run the oil 6-7000 miles between changes.

[ihookem]

Go with the thinner oil for starting and go with full synthetic for starting and it can take more heat. I also use Amsoil and very happy with it . Shootall changes much more than I do though. If you go synthetic you don't need to change very often according to my oil test results.

[Empty Quiver]

If it were me I would get 5W-30 Mobil 1 and be done with it. The only exception might be if that Bronco is really loose and sees any towing. The newer stuff is built to tighter tolerances, the oil is better than ever, and fuel milage is worth something. If super simple is the goal use the 5w-30 in the Bronco even if loose and just pour in a bottle of Lucas oil additive that will thicken it right up.

[BBF]

 10-40 for everything with the exception of the Suzuki Samurai I had which was called upon to do some heavy work for a 1400 ccm motor. That vehicle ran on 20-50 after break in

[SHOOTALL]

I believe temp range has alot to do with it also. 

[Rex in OTZ]

The best thing is to determine your oil requirements,what do you expect it to do, for how long and in what conditions?, do you use block heaters? do they sit in a cold or heated garage?, is there a lengthly commute? how long between uses do they sit?
to better understand the oil and how it is effected in the engine I recoment wikipedia search 'engine oil viscosity'
Mabe even synthetic oil as well.

Assuming because its synthetic doesnt mean your free of damageing in cold starts.
Company had a 2000's era ford ranger with a 4.0 gas engine, one the supervisors believed that since the engine was serviced with Moibel oil 0W30 that no preheat was required....long story short yes you can start a engine at -30F and it will start, but at what cost?........for us the cost of pulling the heads and replaceing torn valve wiper boots as they tore instead of flexing, also seen the main crank seals start to drool so oil loss is a big danger(check the dip stick). best thing to realize is your going to spend money in winter running a vehicle, the added cost of block heater/battery blanket/tranny heat pad is expensive.......in compared costs of fixing the engine from cold damage is allot more+ down time of not having it when you need it.

[rdmallory]

If the Ford is the 4.6L stay with 5w 30 in it or you will have cam chain noise when you first start it up.

Doug