We have (5) 34SG engines and run a 50/50 glycol mix. We can have ambient temps as low as -30°F. We are using polypropylene glycol with an organic corrosion inhibitor (non-toxic). We did experience 95°F temps this summer and all of our engines derated, but it was not as dramatic as we anticipated. We only ended up derating to roughly to 8.0-8.7 mW from our normal output of 9.6mW. We found that manually running the radiator fans to 100% helped stave off derating. We are also in the process of installing a soft water spray mist system on our radiators, in an effort to increase their cooling efficiency. We have found that a cooling mist system can lower radiator output cooling water by as much as 10°F. When our cooling mist system is running our engines do not derate.