I read somewhere (owners manual or on the oil container) that you shouldn't do this. However if I was somewhere not near a store where I could buy some oil and I was a quart or two low I would put in anything I had. Chuck
Chuck and Pat Comer 1996 Southwind 30 ft. 1996 Ford 460 F53 SuperDuty Chassis, Safe-T-Steer, Bilstein Shocks
If you have a good working relationship with an auto parts store, I am sure they would be happy to swap out one weight oil for another, though within the same brand, I am not sure of any reason they can't be mixed. It would depend on the viscosity of oil speced for your vehicle.
Late model vehicles have much closer bearing tolerances and using a heavier viscosity oil will at a minimum cause extra friction and loss of MPG and will also cause added heat due to the friction. There was even a technical service bulletin on one car we owned where the first action to be taken for rough idle was to change to the proper (in that case 5-30) oil. They found 20-40 or straight weight oils raised friction to where the engines did not idle properly.
In general it is not a good practice to mix different weights of oil. If the oil is low and only a different weight is available then it is a whole lot better than driving with low oil. Change it as soon as possible. GM at one time was very particular about the weight of oil used in their engines. Good luck
I was told by someone at Texaco, a long time ago, that if you do what you said, and the "type" (SE or SF, etc.) on the container is the same, no harm is done. He went on to say that if you mixed it half and half of each type, you would literally end up with 7.5 x 30. In your case, with simply one quart, it should be hardly noticeable, "viscosity wise."
There was some discussion of not mixing single viscosity oils like SAE 30 with 5w30, but I don't recall the discussion. Even then however, if I was low enough on oil to possibly damage the engine, and all I had was 30 weight, it would definitely be added, and then get (in a timely manner) to where you can change the oil.
5W30 oil has a higher viscosity at higher temperatures than 5W20. One of our cars, a 1999 Honda Accord V-6 requires 5W30, the other, a 2001 Honda Accord V-6 requires 5W20. I run 5W30 in both with no problems.
Multi grade oil was mfg so that at start up the oil would flow easier (Ex: 5W). As the engine warmed up the oil would change to the higher viscosity number or 30W as in 5W-30W. I see no harm in putting in a higher viscosity if the outside temperature is above freezing.
5W-20 was developed to meet new engine standards (IE: API SL,ILSAC GF-3) and also used in newer & older models to decrease emissions. Unless you have over 75K miles on your vehicle when you change to 5W-20, or started with 5W-20 I would recommend staying with it.
Ford SAE 5W-20 recommendations TSB 02-1-9 (also applies to some Honda & Mazda vehicles)
Ford has updated its viscosity recommendations for many vehicles with the availability of API SL classification oils. The latest recommendation is to use SAE 5W-20 oils in most 2001 engine applications, and in many earlier applications that used SAE 10W-30 and SAE 5W-30. This bulletin updates TSB #99-8-16, 05/03/99, which changed the recommendation from SAE 10W-30 to SAE 5W-30 oil for many earlier Ford vehicles. SAE 5W-30 oil continues to be recommended for any 1989 and later Ford engine/vehicle combination not listed in Table 1.
Table 1. Recommended Ford engines/vehicles for SAE 5W-20 oil (in order of increasing displacement)
API SL, ILSAC GF-3, Ford WSS-M2C153-H
AMSOIL full synthetic XLM 7500 mile Severe Service
2001 2.0-L Zetec Focus
2001 2.0-L SPI Focus
2001 2.0-L Zetec Escape
2001 2.0-L SPI Escort
2001 2.0-L Zetec Escort ZX2
1995-2000 2.5-L Contour/Mystique
1999-2001 2.5-L Cougar
1996-2001 3.0-L 4V Taurus/Sable
1999-2001 3.0-L (Vulcan) Ranger (flexible fuel and gasoline), Windstar, Taurus/Sable (flexible fuel and gasoline)
2000-2001 3.0-L Lincoln LS
2001 3.0-L Escape
1996-1997 3.8-L Thunderbird/Cougar
1996-2001 3.8-L Mustang
1996-2001 3.8-L SPI Windstar
1997-2001 4.2-L SPI F-150 (under 8500 GVW only), Econoline
1996-2001 4.6-L 2V Mustang
1992-2001 4.6-L Crown Victoria/Grand Marquis
1991-2001 4.6-L Town Car
1994-1997 4.6-L 2V Thunderbird/Cougar
1996-2001 4.6-L 4V Mustang Cobra
1995-2001 4.6-L Continental
1993-1998 4.6-L 4V Mark VIII
1998-2001 5.4-L 2V/4V Navigator
1997-2001 . 4.6-L 2V Triton F-150/250 (under 8500 GVW only), Econoline, Expedition
1997-2001 5.4-L 2V F-150/250 (under 8500 GVW only), Expedition, E-150/250/350, E-350 chassis/RV/cutaway
2000-2001 5.4-L Excursion
1997-2001 6.8-L E-250/350, E-350 chassis/RV/cutaway
1999-2001 6.8-L Super Duty F-250 HD/350/450/550 motorhome
2000-2001 6.8-L Excursion
Table 2. Recommended 2001 Ford engines/vehicles for SAE 5W-30 oil (in order of increasing displacement) 2.5-L Ranger
3.9-L Lincoln LS
4.0-L Ranger, Explorer/Mountaineer, Explorer Sport, Explorer Sport Trac
These vehicles were factory-filled with SAE 5W-30 oil.
I have always heard through my 25 years of driving that mixing different viscosity grades of oil in any vehicle is not a good thing and would raise oil consumption. Although oil consumption is pretty much not an issue with the new cars and trucks like the 2002 ford ranger I have.
Does anyone know the difference between 5w20 and 5w30 oils. My new truck recommends 5w20 and I would like to know the difference between the two. Any suggestions?