Hello- New to the forum so thanks for any advice provided. Just picked up a 1972 Chevy pickup with the 250ci inline 6, loving it. Want to do an oil change for my own maintenance records. Previous owner uses 10w-40 Oreilly brand oil. We live in El Paso, TX where it gets very hot. What are your thoughts of moving to a Diesel 15w-40 with zinc additive? Or stay at the 10w40 conventional with zinc additive? I would like to use Mobile 1 10w-40 high mileage with a quart of lucas zinc additive for my first oil change. I will use an NGK filter as well. Any recommendations?

I also have a flat spot upon acceleration. Its not bad, but it will burp for a second and then catch fine. It also takes a good 5-10 minutes before I am able to drive it to warm up before I am able to drive away. If I try and let it warm up only for a couple of minutes, it will just drive once I put my foot on the pedal. Is this common with these engines? Just cold natured?

Thanks again for any recommendations and help.

Also, what antifreeze is recommended? Previous owner just used the basic 50/50 yellow.

I would stay with a 15W-40 rather than a 10W-40. Do not worry about zinc or use a zinc additive as there is enough zinc in any good 5W-30, 10W30 or 15W40 oil.
The 250 engine valve springs are low tension so the lifer to camshaft pressure is very low.
A 15W40 oil will be fine as is and I would not use any LUCAS product as a good oil has all the necessary additives and mixing in more magic stuff could do more harm than good.
Any name brand oil filter is fine .
I would suspect the carburetor is probably due for a rebuild.

The 250 engine is not an oil fussy engine.

I drove a 71 250 for years. Like Gene said the carb should be rebuilt. Mine had a flat spot at one time that was cured with increasing the timing a bit.

I raced the 250 for years. Wonderful engine with seven main bearings. I would bore it out 1/8 and install 327 pistons. With an isky 505 cam and 750 holly, Clifford intake and exhaust. We were track point champion at Canfield Speedway two years in a row.

Sounds like you have a real solid truck. I agree with the advice being offered. 15w-40 regular oil will work very well for you especially in your climate. Yes, the carb probably needs rebuilt more to clean it out than any other reason.

If you are not sure of the service history on the truck it might be a good time to do what is often called "baselining" the vehicle. Over the next few months change all the fluids (including flushing the brakes), replace all the cooling system hoses, and do a full tune-up (plugs, points, ignition wires, distributor cap and rotor). Then you know the service history!