Best lube to use to install fuel injectors?

Since it is an Italian car perhaps extra virgin olive oil.

 

Silicone lubricant grease is the best type for rubber O-rings and seals since most are made from synthetic rubbers such as nitrile, EPDM or Neoprene

Petroleum based lubes can adversely affect the material, i.e swell, harden or make them weaker.

 

I agree with hessank. Probably one of if not the best choice based on chemical reactivity/compatibility charts. Pool system o-ring grease obtained at big box stores or pool stores seems to be about the best price I’ve seen for a substantial sized tube. Dealership parts, dive shops, and autoparts stores often sell smaller packaging for a greater cost, marketed also as weather seal dressing and di-electric grease.

 

Rubber o-rings on injectors are made from rubber that is resistant to fuel (which last I looked was a petroleum product), usually Buna-n, Viton or other synthetic rubber. Any petroleum based grease or synthetic grease will work fine. Silicone products in the engine compartment are a no-no. Fumes from silicone sprays or greases destroy oxygen sensors, hence the oxygen sensor safe RTV silicone sealant products that you see for sale. The minimal amount of silicone grease used to lube an o-ring would probably be fine, but I would not risk it.
Bosch used to recommend regular engine oil or gear oil on the seals to install their injectors.

 

Overthinking the subject.

 

Vaseline is commonly used. Motor oil will be fine too. Not a fan of silicones in the engine bay.

 

LOL

 

Just know EPDM or nitrile become weaker when any petroleum type lubricant/grease is used. That said, injectors don't see incredibly high temps where it would be an issue so don't worry too much about what is used.