Can anyone explain to me why discos start so slow on cold morning? Both of mine start great as long as it's not below 50 degrees overnight, but if it does get below that it cranks so slow, and they both have optima yellow top batteries...

 

What oil are you running? My 2001 D2 cranks about the same. This morning -9C turned over just fine, running 15-40.

 

Not sure, do you have the factory starter on both of them? It's certainly not an issues with all Discoveries as mine cranks the same whether it's 115 in the summer here or 15 in the winter, with 15w-40 oil in it all year round.

Or maybe Optima's Yellow top just isn't as good as they claim. I've never really had any experience with them. All I've ever run was their BlueTop, it was great, but I'm now just running an Interstate truck battery with little to no difference.

 

I'm running rotella 15w40 but it was the same way last winter when I was using another oil and I had a standard dura last battery then too... SW I do have the original starters on both, that had crossed my mind before but like last year, as soon as it warmed back up it started cranking fine again. I guess I could give it a shot. Know of a good replacement starter? And should I try going to the T6 oil for the winter months?

 

I'm actually just running a re-manufactured one with a lifetime warranty from O'Reilly's surprisingly enough, but I've had it on there for many years now without issue, and I remember when I installed it, it had noticeably more torque than the original.

Not sure even slightly if that is your problem, but it could be. Also I wouldn't bother changing oil type/weight during the winter. It's be negative degrees in places and I've never had issue with the 15w-40 Rotella.

 

Any reman starter will be fine. It's cool that O'Reilly's has them; it always amazes me how many of our parts are hard to find locally.

You should run 5w-40 during the winter. In fact, you should run it all the time. 90% of engine wear happens when you first crank it, and thinner oil circulates faster to help prevent this wear. Cold 15w-40 is so thick you are certainly increasing start-up wear by running it. Even during the summer, the more rapid circulation of a thinner oil will help prevent wear.

Beside the wear issues, T6 ran much quieter and smoother in my truck than Rotella T (15w-40). I'm now running M1 5w-40 TDT, but I'd run T6 again. However, I'll never go back to Rotella T. When I first put the T in, I was amazed how bad the motor sounded, and it only got worse til I changed it 2500 miles later because I couldn't stand it anymore. Tons more valve train and lifter noise, and it just ran rougher. As soon as I put in the M1 everything quieted back down again.

 

Cool, thanks a lot guys, I appreciate the feedback. I suppose I'll start by getting a new starter....