Subject: [TR] PSI vs Octane

From: Bill Beecher <[email-masked]>
Date: Fri, 17 Apr 2026 17:06:57 -0500

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Good evening all,
I have always run regular 87 octane in my TR3(=E2=80=9866 TR4 motor), no kno=
cks or pings.  Don=E2=80=99t know what got me to thinking but there has to b=
e a relation between compression psi and the octane rating I should use.   M=
y compression across all four is 175-180, would I be getting improved perfor=
mance from a higher octane gas? Or just wasting $$ ?
All the best,
Bill B
TS30766L

=E2=80=9CThe harder I work, the luckier I get=E2=80=9D  H. Ford=

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v=3D"content-type" content=3D"text/html; charset=3Dutf-8"></head><body dir=3D=
"auto">Good evening all,<div>I have always run regular 87 octane in my TR3(=E2=
=80=9866 TR4 motor), no knocks or pings. &nbsp;Don=E2=80=99t know what got m=
e to thinking but there has to be a relation between compression psi and the=
 octane rating I should use. &nbsp; My compression across all four is 175-18=
0, would I be getting improved performance from a higher octane gas? Or just=
 wasting $$ ?<div>All the best,</div><div>Bill B</div><div>TS30766L<br><div>=
<br id=3D"lineBreakAtBeginningOfSignature"><div dir=3D"ltr">=E2=80=9CThe har=
der I work, the luckier I get<span style=3D"font-size: 19pt;">=E2=80=9D &nbs=
p;H. Ford</span></div></div></div></div></body></html>=

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** [email-masked] **

Archive: http://www.team.net/pipermail/triumphs  http://www.team.net/archive

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From: bill beecher <[email-masked]>
Date: Fri, 17 Apr 2026 17:09:34 -0500

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Good evening all,

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v=3D"content-type" content=3D"text/html; charset=3Dutf-8"></head><body dir=3D=
"auto">Good evening all,<br><div dir=3D"ltr"><div>I have always run regular 8=
7 octane in my TR3(=E2=80=9866 TR4 motor), no knocks or pings. &nbsp;Don=E2=80=
=99t know what got me to thinking but there has to be a relation between com=
pression psi and the octane rating I should use. &nbsp; My compression acros=
s all four is 175-180, would I be getting improved performance from a higher=
 octane gas? Or just wasting $$ ?<div>All the best,</div><div>Bill B</div><d=
iv>TS30766L<br><div><br id=3D"lineBreakAtBeginningOfSignature"><div dir=3D"l=
tr">=E2=80=9CThe harder I work, the luckier I get<span style=3D"font-size: 1=
9pt;">=E2=80=9D &nbsp;H. Ford</span></div></div></div></div></div></body></h=
tml>=

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From: <[email-masked]>
Date: Fri, 17 Apr 2026 18:48:40 -0500

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Bill,

=20

It is the compression ratio of the engine, not the cylinder compression, =
that is related to octane rating.

=20

Generally, the higher compression ratio, the more need for high octane =
fuel.

My Healey has a 10:1 compression ratio, so I add an octane booster to =
each tank of gas.

My TR3 engine has whatever the factory compression ratio was, so the =
octane rating is not that important. But, I still put =
=E2=80=9CPremium=E2=80=9D gasoline in it because that is all that is =
available near me that does not contain corn.=20

=20

All that said, in theory, most engine will perfume better with higher =
octane fuel, and they should get better fuel milage as well.=20

Non ethanol gas will result in around 10 percent better fuel milage.

But if you are running gas with ethanol, I doubt the additional cost of =
=E2=80=9CPremium=E2=80=9D fuel it is worth it for =
=E2=80=9Cnormal=E2=80=9D driving.=20

=20

Check the owner=E2=80=99s manual for the TR4 and see what it recommends =
for fuel octane rating.

  Ron

=20

From: Triumphs <[email-masked]> On Behalf Of Bill =
Beecher
Sent: Friday, April 17, 2026 5:07 PM
To: Randall <[email-masked]>
Subject: [TR] PSI vs Octane

=20

Good evening all,

I have always run regular 87 octane in my TR3(=E2=80=9866 TR4 motor), no =
knocks or pings.  Don=E2=80=99t know what got me to thinking but there =
has to be a relation between compression psi and the octane rating I =
should use.   My compression across all four is 175-180, would I be =
getting improved performance from a higher octane gas? Or just wasting =
$$ ?

All the best,

Bill B

TS30766L

=20

=E2=80=9CThe harder I work, the luckier I get=E2=80=9D  H. Ford

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link=3D"#467886" vlink=3D"#96607D" style=3D'word-wrap:break-word'><div =
class=3DWordSection1><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>Bill,<o:p></o:p=
></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'><o:p>&nbsp;</o:=
p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>It is the =
compression ratio of the engine, not the cylinder compression, that is =
related to octane rating.<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'><o:p>&nbsp;</o:=
p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>Generally, the =
higher compression ratio, the more need for high octane =
fuel.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>My Healey has =
a 10:1 compression ratio, so I add an octane booster to each tank of =
gas.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>My TR3 engine =
has whatever the factory compression ratio was, so the octane rating is =
not that important. But, I still put =E2=80=9CPremium=E2=80=9D gasoline =
in it because that is all that is available near me that does not =
contain corn. <o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'><o:p>&nbsp;</o:=
p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>All that said, =
in theory, most engine will perfume better with higher octane fuel, and =
they should get better fuel milage as well. <o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>Non ethanol =
gas will result in around 10 percent better fuel =
milage.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>But if you are =
running gas with ethanol, I doubt the additional cost of =
=E2=80=9CPremium=E2=80=9D fuel it is worth it for =
=E2=80=9Cnormal=E2=80=9D driving. <o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'><o:p>&nbsp;</o:=
p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>Check the =
owner=E2=80=99s manual for the TR4 and see what it recommends for fuel =
octane rating.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'> =
<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'>=C2=A0=C2=A0Ron=
<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Arial",sans-serif'><o:p>&nbsp;</o:=
p></span></p><div><div style=3D'border:none;border-top:solid #E1E1E1 =
1.0pt;padding:3.0pt 0in 0in 0in'><p class=3DMsoNormal><b><span =
style=3D'font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span><=
/b><span style=3D'font-size:11.0pt;font-family:"Calibri",sans-serif'> =
Triumphs &lt;[email-masked]&gt; <b>On Behalf Of =
</b>Bill Beecher<br><b>Sent:</b> Friday, April 17, 2026 5:07 =
PM<br><b>To:</b> Randall =
&lt;[email-masked]&gt;<br><b>Subject:</b> [TR] PSI vs =
Octane<o:p></o:p></span></p></div></div><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><p class=3DMsoNormal>Good evening =
all,<o:p></o:p></p><div><p class=3DMsoNormal>I have always run regular =
87 octane in my TR3(=E2=80=9866 TR4 motor), no knocks or pings. =
&nbsp;Don=E2=80=99t know what got me to thinking but there has to be a =
relation between compression psi and the octane rating I should use. =
&nbsp; My compression across all four is 175-180, would I be getting =
improved performance from a higher octane gas? Or just wasting $$ =
?<o:p></o:p></p><div><p class=3DMsoNormal>All the =
best,<o:p></o:p></p></div><div><p class=3DMsoNormal>Bill =
B<o:p></o:p></p></div><div><p =
class=3DMsoNormal>TS30766L<o:p></o:p></p><div><p =
class=3DMsoNormal><o:p>&nbsp;</o:p></p><div><p =
class=3DMsoNormal>=E2=80=9CThe harder I work, the luckier I get<span =
style=3D'font-size:19.0pt'>=E2=80=9D &nbsp;H. =
Ford</span><o:p></o:p></p></div></div></div></div></div></body></html>
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