heading on a 2600 mile trip (mostly interstate) on saturday. just changed the oil on my 2003 5.4 tonight with penzoil 5w-30. the book says 5w-20, but i allready had the 5w-30, and figured with the hot weather and long hiway drive the heavierweight might be wise. am i wrong? i even thought about 10w-30. am i gambling? it has 42,000 miles on it. just got it a month ago, and this is my first oil change. if anyone is concerned please post, i'd rather change it than ruin it!

 

Me and many others have been using 5w30 with no problems. I wouldn't go up to a 10w30 however. I personally use Mobil 1 and change the oil every 6000 miles. I just can't bring myself to go 10,000 to 20,000 with synthetic oil.

 

As far as I understand it correctly the 5w-20 is mostly to do with fuel economy. I may be wrong, and frequently am!

 

It is also my understanding that a lot of car makers are going to lighter weight oils to try and improve mileage. If you live in hotter climates you should be ok going to slightly heavy weight oil.

Be careful going too heavy or too light though. Hydraulics is just like electricity, it takes the path of least resistance. There are numerous oil passages all over the engine. These are all taken into account regarding the flow rate of the oil in the block when the engine is designed. If you go too light over stock, then oil pressure might drop too much to push oil through the farthest and/or highest passages. If you go too heavy you will get oil to all of the passages, but you may not get enough flow to lubricate properly. Temperature also plays a part in the flow of the oil. If you live in a really hot or really cold environment, ask around and what other people are running, but I wouldn't go up or down by more than one weight.

Check out this. A good article about oil weights.

 

this trip will be from central ky to southern co. i figured the temps would be warm, and alot of 75 mph driving for hours on end (20 hours driving time) plan on changing it back to 5w-20 when i get back in prep for winter.

 

Hey to all. I'm a newbie here, bought an 05 Supercrew XLT, 5.4.
As an aircraft mech here is some info I have read. The lighter multi-weight oils, like 5w-20, are to circulate throughout the engine quicker than the 10w-30 oils. This in theory is to disapate the heat and deposits picked up by the oil quicker. Will the thicker oils hurt? Who knows, the overhead cam design does have tighter tollerances than the older style engines. I plan to use Mobil 1 5w30 and change at 3-5k.
My thanks to all who post here, as I have been watching lurking here while I was truck shopping.

 

Good luck with the new truck! I've been slowly modding mine for about 5 years now. Usually when something wears out, I replace it with better. Paid mine off a while ago, but lately she is draining the repair funds! Did the rear end, and 20K later had to do it again. That's what I get for going with the cheapest shop in town (only $900)! They repaired it and didn't flush out the housing. All those chips ruined it in short order. The only thing salvagable was the housing, ring gear, pinion gear, and axle shafts. Carrier and LS was chewed up, plus all bearings, seals, and pinion flange. Upgraded the diff cover at same time and did a shift kit for a grand total of another $1200. Now I have the dreaded TC shudder ($900). Will have to take it in to find out if it is the TC or the TC solenoid. Hopefully it is the solenoid. Also needed new shocks $350 (Edelbrock). Exhaust is leaking and needs to be replaced $460 (Magnaflow), plus my front seat has a spring stabbing me in the butt if I get in the truck wrong ($1000 new performance seats)! I keep having to tell myself that maintenance/repair is expensive, but still cheaper than a new car payment! Just trying to figure out if it is worth the hassle too! I do love my truck though, especially with the new HID's. Took my friend for a ride who has a supercharged M3 and he was very impressed with the lighting. Now if it was just as fast as his M3 .....

 

Your 2003 has the same engine as my 2000. The owners manuel says 5-30 mc synthetic blend in mine, weight wise you should be fine. I would stick with a blend in the future.