<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">It’s all about compression, higher compression needs higher octane to prevent the pinging/knocking that will damage the pistons. That said, I usually run regular grade in my stock TR3 or maybe step up to mid grade during the hot Texas summer months. <div>Bill B<br><br><div id="AppleMailSignature" dir="ltr"><span style="background-color: rgba(255, 255, 255, 0);">Sent from my Handspring Treo</span></div><div dir="ltr"><br>On Sep 23, 2018, at 9:51 AM, Geo Hahn <<a href="mailto:ahwahneetr@gmail.com">ahwahneetr@gmail.com</a>> wrote:<br><br></div><div dir="ltr"><div dir="ltr">Terry -<div><br></div><div>I rather think it was due to compression ratio more than anything else. But you may just have to experiment a bit to see what works (adjusting advance, listening for ping).</div><div><br></div><div>My TR4 uses premium at off-brand stations but seems okay with regular from Shell or Chevron. My TR3A doesn't seem to care what I put in it, runs fine on almost anything.</div><div><br></div><div>Geo</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Sep 23, 2018 at 6:26 AM, TERRY SMITH <span dir="ltr"><<a href="mailto:terryrs@comcast.net" target="_blank">terryrs@comcast.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Just curious. Why is Premium gasoline recommended for a TR3 (and I suppose other Triumphs?)while regular is just fine for other vintage cars. I know it's to prevent knocking, but how and why? Does it have to do with being a short-stroke engine or something? <br>
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Thanks, everyone,<br>
Terry<br>
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